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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2017	Feb. 15, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Trading Symbol	SGMO
Entity Registrant Name	SANGAMO THERAPEUTICS, INC
Entity Central Index Key	0001001233
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		86,338,976
Entity Public Float			$ 734,155,954

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 49,826	$ 22,061
Marketable securities	193,482	120,474
Interest receivable	240	224
Accounts receivable	3,343	4,972
Prepaid expenses and other current assets	1,506	1,849
Total current assets	248,397	149,580
Marketable securities, non-current	1,012
Property and equipment, net	31,066	6,557
Goodwill	1,585	1,585
Other assets	4,681	169
Total assets	286,741	157,891
Current liabilities:
Accounts payable and accrued liabilities	11,035	6,261
Accrued compensation and employee benefits	5,479	2,885
Deferred revenues	28,345	4,145
Total current liabilities	44,859	13,291
Deferred revenues, non-current	29,244	4,460
Build-to-suit lease obligation	24,738	3,945
Total liabilities	98,841	21,696
Commitments and contingencies
Stockholders' equity:
Common stock, $0.01 par value; 160,000,000 shares authorized, 85,598,534 and 70,871,902 shares issued and outstanding at December 31, 2017 and December 31, 2016, respectively	856	709
Additional paid-in capital	682,809	576,377
Accumulated deficit	(495,479)	(440,911)
Accumulated other comprehensive income (loss)	(286)	20
Total stockholders' equity	187,900	136,195
Total liabilities and stockholders' equity	$ 286,741	$ 157,891

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	160,000,000	160,000,000
Common stock, shares issued	85,598,534	70,871,902
Common stock, shares outstanding	85,598,534	70,871,902

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Collaboration agreements	$ 35,960	$ 18,881	$ 37,844
Research grants	607	508	1,695
Total revenues	36,567	19,389	39,539
Operating expenses:
Research and development	65,728	65,618	67,198
General and administrative	27,200	26,330	19,197
Total operating expenses	92,928	91,948	86,395
Loss from operations	(56,361)	(72,559)	(46,856)
Interest and other income, net	1,793	887	431
Loss before income taxes	(54,568)	(71,672)	(46,425)
Benefit from income taxes		14	5,722
Net loss	$ (54,568)	$ (71,658)	$ (40,703)
Basic and diluted net loss per share	$ (0.70)	$ (1.02)	$ (0.58)
Shares used in computing basic and diluted net loss per share	78,084	70,553	69,757

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (13,091)	$ (12,354)	$ (12,491)	$ (16,632)	$ (9,624)	$ (18,965)	$ (26,575)	$ (16,494)	$ (54,568)	$ (71,658)	$ (40,703)
Change in unrealized gain (loss) on available-for-sale securities, net of tax									(306)	20	25
Comprehensive loss									$ (54,874)	$ (71,638)	$ (40,678)

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income/ (Loss) [Member]
Beginning Balances at Dec. 31, 2014	$ 206,633	$ 690	$ 534,518	$ (328,550)	$ (25)
Beginning Balances, shares at Dec. 31, 2014		69,062,394
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax	4,348	$ 12	4,336
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax, shares		1,164,033
Issuance of common stock under employee stock purchase plan	$ 911	$ 1	910
Issuance of common stock under employee stock purchase plan, shares	128,181	128,181
Stock-based compensation	$ 11,730		11,730
Claims settlement under Section 16(b), net of tax benefit	9,495		9,495
Comprehensive loss:
Net unrealized gain (loss) on marketable securities, net of tax	25				25
Net loss	(40,703)			(40,703)
Comprehensive loss	(40,678)
Ending Balances at Dec. 31, 2015	192,439	$ 703	560,989	(369,253)
Ending Balances, shares at Dec. 31, 2015		70,354,608
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax	(481)	$ 3	(484)
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax, shares		314,583
Issuance of common stock under employee stock purchase plan	$ 818	$ 3	815
Issuance of common stock under employee stock purchase plan, shares	202,711	202,711
Stock-based compensation	$ 15,057		15,057
Comprehensive loss:
Net unrealized gain (loss) on marketable securities, net of tax	20				20
Net loss	(71,658)			(71,658)
Comprehensive loss	(71,638)
Ending Balances at Dec. 31, 2016	$ 136,195	$ 709	576,377	(440,911)	20
Ending Balances, shares at Dec. 31, 2016	70,871,902	70,871,902
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax	$ 15,099	$ 21	15,078
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax, shares		2,101,489
Issuance of common stock under employee stock purchase plan	$ 818	$ 2	816
Issuance of common stock under employee stock purchase plan, shares	253,994	253,994
Issuance of common stock under public offering, net of issuance costs	$ 81,573	$ 124	81,449
Issuance of common stock under public offering, net of issuance costs, shares		12,371,149
Stock-based compensation	9,089		9,089
Comprehensive loss:
Net unrealized gain (loss) on marketable securities, net of tax	(306)				(306)
Net loss	(54,568)			(54,568)
Comprehensive loss	(54,874)
Ending Balances at Dec. 31, 2017	$ 187,900	$ 856	$ 682,809	$ (495,479)	$ (286)
Ending Balances, shares at Dec. 31, 2017	85,598,534	85,598,534

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities:
Net loss	$ (54,568)	$ (71,658)	$ (40,703)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	1,498	997	988
Amortization of premium (discount) on marketable securities	(673)	221	827
Net loss on disposal of property and equipment	12
Stock-based compensation	9,089	15,057	11,730
Change in fair value of contingent consideration liability			(1,800)
Intangible impairment			1,870
Benefit from income taxes		(14)	(5,722)
Other	80	99
Net changes in operating assets and liabilities:
Interest receivable	(16)	83	116
Accounts receivable	1,629	(2,144)	7,847
Prepaid expenses and other assets	(669)	(1,112)	376
Accounts payable and accrued liabilities	3,219	(2,335)	(764)
Accrued compensation and employee benefits	2,594	137	(105)
Deferred revenues	48,984	(5,214)	(8,380)
Net cash provided by (used in) operating activities	11,179	(65,883)	(33,720)
Investing Activities:
Purchases of marketable securities	(252,328)	(218,640)	(257,988)
Maturities of marketable securities	178,675	237,497	337,861
Purchases of property and equipment	(3,751)	(732)
Lease commitments	(3,500)
Acquisition of Ceregene, Inc. net of cash received			(2,411)
Net cash (used in) provided by investing activities	(80,904)	18,125	77,462
Financing Activities:
Proceeds from public offering of common stock, net of issuance costs	81,573
Taxes paid related to net share settlement of equity awards	(654)	(776)	(1,546)
Proceeds from issuance of common stock	16,571	1,113	6,804
Claims settlement under Section 16(b)			14,452
Net cash provided by financing activities	97,490	337	19,710
Net increase (decrease) in cash and cash equivalents	27,765	(47,421)	63,452
Cash and cash equivalents, beginning of period	22,061	69,482	6,030
Cash and cash equivalents, end of period	49,826	22,061	$ 69,482
Property and Equipment [Member]
Supplemental disclosure of noncash investing activities:
Property and equipment/build-to-suit leases included in accrued liabilities and obligation	1,214
Build-to-Suit Leases [Member]
Supplemental disclosure of noncash investing activities:
Property and equipment/build-to-suit leases included in accrued liabilities and obligation	$ 20,793	$ 3,876

Organization and Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Organization and Summary of Significant Accounting Policies

NOTE 1 – ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Overview

Sangamo Therapeutics, Inc. was incorporated in the State of Delaware on June 22, 1995 and changed its name from Sangamo Biosciences, Inc. in January 2017 (the Company or Sangamo). Sangamo is focused on the research, development and commercialization of novel therapeutic strategies for unmet medical needs. Sangamo’s genome editing and gene regulation technology platform is enabled by the engineering of a class of transcription factors known as zinc finger DNA-binding proteins (ZFPs). Potential applications of Sangamo’s technology include development of human therapeutics, plant agriculture and enhancement of pharmaceutical protein production. Sangamo will require additional financial resources to complete the development and commercialization of its products including ZFP Therapeutics.

Sangamo is currently working on a number of long-term development projects that will involve experimental technology. The projects may require several years and substantial expenditures to complete and ultimately may be unsuccessful. The Company plans to finance operations with available cash resources, collaborations and strategic partnerships funds, research grants and from the issuance of equity or debt securities. Sangamo believes that its available cash, cash equivalents and investments as of December 31, 2017, along with expected revenues from collaborations, strategic partnerships and research grants, will be adequate to fund its operations at least through the next twelve months from the date the financial statements are issued. Sangamo will need to raise substantial additional capital to fund subsequent operations and complete the development and commercialization of its products. Additional capital may not be available on terms acceptable to the Company, or at all. If adequate funds are not available, or if the terms of potential funding sources are unfavorable, the Company’s business and ability to develop its technology and ZFP Therapeutic products would be harmed. Furthermore, any sales of additional equity securities may result in dilution to the Company’s stockholders, and any debt financing may include covenants that restrict the Company’s business.

Basis of Presentation

The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. The consolidated financial statements include the accounts of Sangamo and its wholly-owned subsidiaries, Ceregene and Gendaq Limited, after elimination of all intercompany balances and transactions.

Business Combinations

The Company accounts for acquisitions in accordance with Accounting Standards Codification (ASC) Topic 805, Business Combinations (ASC Topic 805). ASC Topic 805 establishes principles and requirements for recognizing and measuring the total consideration transferred to and the assets acquired, liabilities assumed and any non-controlling interests in the acquired target in a business combination. ASC Topic 805 also provides guidance for recognizing and measuring goodwill acquired in a business combination; requires purchased in-process research and development to be capitalized at fair value as an intangible asset at the time of acquisition; requires acquisition-related expenses and restructuring costs to be recognized separately from the business combination; expands the definition of what constitutes a business; and requires the acquirer to disclose information that users may need to evaluate and understand the financial effect of the business combination.

Cash and Cash Equivalents

Sangamo considers all highly-liquid investments purchased with original maturities of three months or less at the purchase date to be cash equivalents. Cash and cash equivalents consist of deposits in money market investment accounts.

Marketable Securities

Sangamo classifies its marketable securities as available-for-sale and records its investments at estimated fair value based on quoted market prices or observable market inputs of almost identical assets, with the unrealized holding gains and losses included in accumulated other comprehensive income.

The Company’s investments are subject to a periodic impairment review. The Company recognizes an impairment charge when a decline in the fair value of its investments below the cost basis is judged to be other-than-temporary. The Company considers various factors in determining whether to recognize an impairment charge, including the length of time and extent to which the fair value has been less than the Company’s cost basis, the financial condition and near-term prospects of the investee, and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in the market value. Realized gains and losses on available-for-sale securities are included in other income, which is determined using the specific identification method.

Fair Value Measurements

The carrying amounts for financial instruments consisting of cash and cash equivalents, accounts receivable, accounts payable and accrued liabilities approximate fair value due to their short maturities. Marketable securities and contingent consideration liabilities are stated at their estimated fair values. The counterparties to the agreements relating to the Company’s investment securities consist of the US Treasury, governmental agencies, various major corporations and financial institutions with high credit standing.

Property and Equipment

Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is calculated using the straight-line method based on the estimated useful lives of the related assets (generally three to five years). For leasehold improvements, amortization is calculated using the straight-line method based on the shorter of the useful life or the lease term. The Company reviews its property and equipment for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable.

Use of Estimates

The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the financial statements and the accompanying notes. On an ongoing basis, management evaluates its estimates, including critical accounting policies or estimates related to revenue recognition, clinical trial accruals, and stock-based compensation. Estimates are based on historical experience and on various other market specific and other relevant assumptions that the Company believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results could differ from those estimates. During the fourth quarter of 2016, we revised our estimated performance period under the Bioverativ license agreement from June 2019 to June 2020, which also extended the recognition period of the related up-front payment we received upon entering this agreement (See Note 5). This change decreased revenues by $4.3 million and increased net loss and net loss per share by $0.06 for the year ended December 31, 2016.

Revenue Recognition

Revenues from research activities made under strategic partnering agreements and collaborations are recognized as the services are provided when there is persuasive evidence that an arrangement exists, delivery has occurred, the price is fixed or determinable, and collectability is reasonably assured. Revenue generated from research and licensing agreements typically includes upfront signing or license fees, cost reimbursements, research services, minimum sublicense fees, milestone payments and royalties on future licensee’s product sales.

Multiple Element Arrangements prior to the adoption of ASU No. 2009-13, Revenue Recognition—Multiple Deliverable Revenue Arrangements (ASU 2009-13). For revenue arrangements entered into before January 1, 2011, that include multiple deliverables, the elements of such agreement were divided into separate units of accounting if the deliverables met certain criteria, including whether the fair value of the delivered items could be determined and whether there was evidence of fair value of the undelivered items. In addition, the consideration was allocated among the separate units of accounting based on their fair values, and the applicable revenue recognition criteria are considered separately for each of the separate units of accounting. Prior to the adoption of ASU 2009-13, the Company recognized nonrefundable signing, license or non-exclusive option fees as revenue when rights to use the intellectual property related to the license were delivered and over the period of performance obligations if the Company had continuing performance obligations. The Company estimated the performance period at the inception of the arrangement and reevaluated it each reporting period. Changes to these estimates were recorded on a prospective basis.

Multiple Element Arrangements after the adoption of ASU 2009-13. ASU 2009-13 amended the accounting standards for certain multiple element revenue arrangements to:

•

provide updated guidance on whether multiple elements exist, how the elements in an arrangement should be separated, and how the arrangement consideration should be allocated to the separate elements;

•

require an entity to allocate arrangement consideration to each element based on a selling price hierarchy where the selling price for an element is based on vendor-specific objective evidence, or VSOE, if available; third-party evidence, or TPE, if available and VSOE is not available; or the best estimate of selling price, or ESP, if neither VSOE nor TPE is available; and

•

eliminate the use of the residual method and require an entity to allocate arrangement consideration using the relative selling price method.

For revenue agreements with multiple element arrangements, such as license and development agreements, entered into on or after January 1, 2011, the Company allocates revenue to each non-contingent element based on the relative selling price of each element. When applying the relative selling price method, the Company determines the selling price for each deliverable using VSOE of selling price or TPE of selling price. If neither exists the Company uses ESP for that deliverable. Revenue allocated is then recognized when the basic four revenue recognition criteria are met for each element. The collaboration and license agreements entered into with Shire International GmbH, formerly Shire AG, or Shire, in January 2012, Biogen MA Inc., or Biogen, in January 2014, and Pfizer Inc., or Pfizer, in May and December of 2017, were evaluated under these amended accounting standards.

Additionally, the Company may be entitled to receive certain milestone payments which are contingent upon reaching specified objectives. These milestone payments are recognized as revenue in full upon achievement of the milestone if there is substantive uncertainty at the date the arrangement is entered into that objectives will be achieved and if the achievement is based on the Company’s performance.

Minimum annual sublicense fees are also recognized as revenue in the period in which such fees are due. Royalty revenues are generally recognized when earned and collectability of the related royalty payment is reasonably assured. The Company recognizes cost reimbursement revenue under collaborative agreements as the related research and development costs for services are rendered. Deferred revenue represents the portion of research or license payments received but not earned.

Sangamo’s research grants are typically multi-year agreements and provide for the reimbursement of qualified expenses for research and development as defined under the terms of the grant agreement. Revenue under grant agreements is recognized when the related qualified research expenses are incurred.

During 2017, revenues related to Pfizer and Bioverativ represented 47% and 34%, respectively, of the Company’s total revenue. During 2016 revenue related to Bioverativ, DAS and Shire represented 46%, 26%, and 17%, respectively, of total revenue. During 2015 revenue related to Shire and Biogen represented 40% and 35%, respectively, of total revenues. Receivables from collaborations are typically unsecured and are concentrated in the biopharmaceutical industry. Accordingly, we may be exposed to credit risk generally associated with biopharmaceutical companies or specific to our collaboration agreements. To date, we have not experienced any losses related to these receivables.

Research and Development Expenses

Research and development costs are expensed as incurred. Research and development expenses consist of direct and research-related allocated overhead costs such as facilities costs, salaries and related personnel costs, and material and supply costs. In addition, research and development expenses include costs related to clinical trials, validation of the Company’s testing processes and procedures as well as related overhead expenses. Research and development costs incurred in connection with collaborator-funded activities are expensed as incurred. Costs to acquire technologies that are utilized in research and development that have no alternative future use are expensed as incurred.

Stock-Based Compensation

The Company measures and recognizes compensation expense for all stock-based payment awards made to Sangamo employees and directors, including employee share options, restricted stock units (RSUs) and employee stock purchases related to the Employee Stock Purchase Plan (ESPP), based on estimated fair values at the award grant date. The fair value of stock-based awards is amortized over the vesting period of the award using a straight-line method.

To estimate the fair value of an award, the Company uses the Black-Scholes option pricing model. This model requires inputs such as expected life, expected volatility and risk-free interest rate. These inputs are subjective and generally require significant analysis and judgment to develop. While estimates of expected life and volatility are derived primarily from the Company’s historical data, the risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant commensurate with the expected life assumption. Further, the Company adopted Accounting Standards Update (ASU) 2016-09 and accounts for forfeitures in the period they occur.

Indefinite-Lived Intangible Assets

As part of the Ceregene acquisition the Company recognized indefinite-lived intangible assets for in-process research and development and goodwill as further discussed below. ASC 350 and related updates require companies to test indefinite-lived intangible assets for impairment annually, and more frequently if indicators of impairment exist. ASC 350 includes an optional qualitative assessment for testing indefinite-lived intangible assets for impairment that permits companies to assess whether it is more likely than not (i.e., a likelihood of greater than 50%) that an indefinite-lived intangible asset is impaired. If a company concludes based on the qualitative assessment that it is not more likely than not that the fair value of an indefinite-lived intangible asset or, in the case of goodwill, that the fair value of the related reporting unit, is less than carrying value, it would not have to determine the asset’s or reporting unit’s fair value, as applicable.

In-Process Research and Development

Intangible assets related to in-process research and development costs, or IPR&D, are considered to be indefinite-lived until the completion or abandonment of the associated research and development efforts. If and when development is complete, which generally occurs if and when regulatory approval to market a product is obtained, the associated assets would be deemed finite-lived and would then be amortized based on their respective estimated useful lives at that point in time. Prior to completion of the research and development efforts, the assets are considered indefinite-lived. During this period, the assets will not be amortized but will be tested for impairment on an annual basis and between annual tests if the Company becomes aware of any events occurring or changes in circumstances that would indicate a reduction in the fair value of the IPR&D projects below their respective carrying amounts. In the first quarter of 2015, the Company decided to discontinue the CERE-110 and CERE-120 clinical trial programs. As such, the probability of achieving projected revenues and cash flows associated with these programs were adversely affected. The Company did not believe the programs have an alternative future use for itself or other market participants. Accordingly, the Company recognized a $1.9 million impairment charge related to these assets during the year ended December 31, 2015, which was recognized as research and development (R&D) in the accompanying consolidated statements of operations.

Goodwill

Goodwill represents the excess of the consideration transferred over the estimated fair values of assets acquired and liabilities assumed in a business combination and is considered to be indefinite-lived. Goodwill is not amortized but is tested for impairment on an annual basis and between annual tests if the Company becomes aware of any events occurring or changes in circumstances that would indicate an impairment of goodwill has occurred. During the fourth quarter of 2017, the Company performed an assessment of the qualitative factors affecting the fair value of its reporting unit and concluded that it was not more likely than not that the fair value of its reporting unit was less than carrying value and that, as a result, it is not more likely than not that goodwill is impaired.

Contingent Consideration Liability

Under the merger agreement with Ceregene, the Company is required to make contingent earn-out payments if the Company grants a third-party license to develop and commercialize certain product candidates acquired from Ceregene, or if the Company commercializes any of such product candidates itself. These earn-out payments will become payable in the period they are earned. In accordance with ASC Topic 805, the Company determined the fair value of this liability for contingent consideration on the acquisition date using a probability-weighted discounted cash flow analysis. During the year ended December 31, 2015, the recognized amount of the liability for contingent consideration decreased by $1.8 million due to the decrease in the probability of incurring potential future royalty payments associated with the impairment of IPR&D assets acquired from Ceregene.

Income Taxes

Income tax expense has been provided using the liability method. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities as measured by the enacted tax rates that will be in effect when these differences reverse. The Company provides a valuation allowance against net deferred tax assets if, based upon the available evidence, it is not more likely than not that the deferred tax assets will be realized.

Net Loss Per Share

Basic net loss per share has been computed by dividing net loss by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share is calculated by dividing net loss by the weighted average number of shares of common stock and potential dilutive securities outstanding during the period.

Because Sangamo is in a net loss position, diluted net loss per share excludes the effects of common stock equivalents consisting of options and restricted stock units, which are all anti-dilutive. All stock options and restricted stock units outstanding were excluded from the calculation of diluted net loss per share for all periods presented. Stock options and restricted stock units outstanding at the end of 2017, 2016 and 2015 were 8,367,628, 9,578,322, and 9,008,185, respectively.

Segments

The Company operates in one segment. Management uses one measure of profitability and does not segregate its business for internal reporting. As of December 31, 2017 and 2016, all of the Company’s assets were maintained in the U.S. For the years ended December 31, 2017, 2016 and 2015, substantially all the Company’s revenues and operating expenses were generated and incurred in the U.S.

Recent Accounting Pronouncements

In March 2016 the Financial Accounting Standards Board (FASB) issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting (Topic 718). The amendments in ASU 2016-09 affect all entities that issue share-based payment awards to their employees and involve multiple aspects of the accounting for share-based payment transactions, including income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The ASU is effective for annual periods beginning after December 15, 2016, and interim periods within those annual periods. Early adoption is permitted for any entity in any interim or annual period. If an entity early adopts the amendments in an interim period, any adjustments should be reflected as of the beginning of the fiscal year that includes that interim period. An entity that elects early adoption must adopt all of the amendments in the same period. The Company adopted the ASU in the first quarter of 2017 and it did not have a material impact on the Company’s consolidated financial statements. The impact of ASU 2016-09 as it relates to stock-based compensation for deferred tax assets and liabilities balances were not material to the Company's consolidated financial statements.

In February 2016 the FASB issued ASU No. 2016-02 (ASU 2016-02) “Leases.” ASU 2016-02 amends a number of aspects of lease accounting, including requiring lessees to recognize almost all leases with a term greater than one year as a right-of-use asset and corresponding liability, measured at the present value of the lease payments. The guidance will become effective for the Company beginning in the first quarter of 2019 with early adoption permitted and will be adopted using a modified retrospective approach. We are evaluating the impact of the adoption of this standard on our consolidated financial statements, and expect our operating lease commitments will be subject to the new standard and recognized as a right-of-use assets and operating lease liabilities upon adoption which will increase our total assets and total liabilities as compared to amounts prior to adoption.

In May 2014 the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606), or ASC 606. This standard outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. The main principle of ASU 2014-09 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. ASU 2014-09 provides companies with two implementation methods: (i) apply the standard retrospectively to each prior reporting period presented (full retrospective application); or (ii) apply the standard retrospectively with the cumulative effect of initially applying the standard as an adjustment to the opening balance of retained earnings of the annual reporting period that includes the date of initial application (modified retrospective application). This guidance is effective for annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period. Under Topic 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. Topic 606 also impacts certain other areas, such as the accounting for costs to obtain or fulfill a contract.

The Company will adopt ASC 606 during the first quarter of 2018 and using the modified retrospective method. The Company has substantially completed its evaluation of the impact of adopting ASC 606 on its contracts with Bioverativ, Shire, DAS, and Sigma (as defined below). The Company’s performance obligations with respect to Shire, DAS and Sigma were substantially complete at December 31, 2017 and any future receipts are contingent upon these counterparties achieving specified development, commercial, and/or sales targets and would be in the form of milestones or royalties, all of which management concluded are constrained at December 31, 2017 as defined under ASC 606. The Company has also performed an assessment of the impact of adopting ASC 606 on its Bioverativ collaboration arrangement and has preliminarily concluded that the timing of the recognition of up-front payments and research and development reimbursements will be decelerated under the new guidance while development and commercialization milestones are constrained at December 31, 2017, as defined under ASC 606. Based on this assessment, management has preliminarily concluded that the transition adjustment to be recognized on January 1, 2018 will be less than $5.0 million and will result in a decrease to accumulated deficit and an increase to deferred revenue at that date as a result of decelerating the recognition of amounts related to research and development reimbursements and up-front payments under ASC 606.

The Company has not completed its assessment of the effect that the adoption of ASC 606 will have on its agreements with Pfizer that were entered into during 2017. The Company has preliminarily concluded that any potential milestone and royalty payments payable under these agreements are constrained at December 31, 2017, as defined under ASC 606, and thus will not result in a change upon adoption of ASC 606 from the accounting for such payments under ASC 605. No revenue or other amounts were recognized in 2017 related to the agreement that was entered into with Pfizer in late December 2017 and, accordingly, management does not expect any amounts to be recognized as part of the January 2018 transition adjustment related to this agreement. During 2017, the Company recognized as revenue $17.0 million of the $70.0 million up-front payment received from agreement the Company entered into with Pfizer in May 2017, the amount and timing of which may change upon adoption of ASC 606.

The estimates of the expected effects of the Company’s adoption of ASU 2014-09 represent management’s best estimates of the effects of adopting ASU 2014-09 at the time of the preparation of this Annual Report on Form 10-K. The actual, final quantitative effects of the adoption of ASU 2014-09 are subject to change from these estimates and such change may be significant, pending the completion of the Company’s assessment in the first quarter of 2018.

Fair Value Measurement

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Fair Value Measurement

NOTE 2 –FAIR VALUE MEASUREMENT

The Company measures certain assets and liabilities at fair value on a recurring basis, including cash equivalents, available-for-sale securities and the contingent consideration liability. Fair value is determined based on a three-tier hierarchy under the authoritative guidance for fair value measurements and disclosures that prioritizes the inputs used in measuring fair value as follows:

Level 1: Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities;

Level 2: Quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability; and

Level 3: Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity).

The fair value measurements of cash equivalents, available-for-sale securities and the contingent consideration liability are identified at the following levels within the fair value hierarchy (in thousands):

	December 31, 2017
	Fair Value Measurements
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	24,290	$	24,290	$	—	$	—
Commercial paper securities		4,595		—		4,595		—
Total		28,885		24,290		4,595		—
Marketable securities:
Commercial paper securities		110,247		—		110,247		—
Corporate debt securities		75,755		—		75,755		—
U.S. government-sponsored entity debt securities		8,492		—		8,492		—
Total		194,494		—		194,494		—
Total cash equivalents and marketable securities	$	223,379	$	24,290	$	199,089		—

	December 31, 2016
	Fair Value Measurements
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	18,992	$	18,992	$	—	$	—
Total		18,992		18,992		—		—
Marketable securities:
Commercial paper securities		23,185		—		23,185		—
Corporate debt securities		10,004		—		10,004		—
U.S. government-sponsored entity debt securities		87,285		—		87,285		—
Total		120,474		—		120,474		—
Total cash equivalents and marketable securities	$	139,466	$	18,992	$	120,474	$	—

Investments

The Company generally classifies its marketable securities as Level 2. Instruments are classified as Level 2 when observable market prices for identical securities that are traded in less active markets are used. When observable market prices for identical securities are not available, such instruments are priced using benchmark curves, benchmarking of like securities, sector groupings, matrix pricing and valuation models. These valuation models are proprietary to the pricing providers or brokers and incorporate a number of inputs, including, listed in approximate order of priority: benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers and reference data including market research publications. For certain security types, additional inputs may be used, or some of the standard inputs may not be applicable. Evaluators may prioritize inputs differently on any given day for any security based on market conditions, and not all inputs listed are available for use in the evaluation process for each security evaluation on any given day.

Contingent Consideration Liability

In August 2013 the Company acquired Ceregene and recorded a liability for the estimated fair value of contingent consideration payments to former Ceregene stockholders, as outlined under the terms of the merger agreement with Ceregene. These contingent payments are owed if the Company grants a third-party license to develop and commercialize certain product candidates acquired from Ceregene, or if the Company commercializes any of such product candidates itself. The fair value of this liability is estimated using a probability-weighted discounted cash flow analysis. Such valuations require significant estimates and assumptions including but not limited to: determining the timing and estimated costs to complete the in-process projects, projecting regulatory approvals, estimating future cash flows and developing appropriate discount rates. The Company has classified this liability as Level 3.

The subsequent changes in the fair value of the contingent consideration liability were recognized as a component of research and development expense line item in the accompanying consolidated statements of operations as operating expenses. During the year ended December 31, 2015, the recognized amount of the liability for contingent consideration decreased by the total fair value of the contingent consideration of $1.8 million due to the decrease in the probability of incurring potential future royalty payments associated with the impairment of IPR&D assets acquired from Ceregene (see Note 6).

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Marketable Securities

12 Months Ended

Dec. 31, 2017

Investments Debt And Equity Securities [Abstract]

Marketable Securities

NOTE 3 – MARKETABLE SECURITIES

The table below summarizes the Company’s cash equivalents and available-for-sale securities (in thousands):

			Gross		Gross
	Amortized		Unrealized		Unrealized			Estimated
	Cost		Gains		(Losses)			Fair Value
December 31, 2017
Cash equivalents:
Money market funds	$	24,290	$	—	$	—		$	24,290
Commercial paper securities		4,595		—		—			4,595
Total		28,885		—		—			28,885
Available-for-sale securities:
Commercial paper securities		110,365		—		(118	)		110,247
Corporate debt securities		75,886		—		(131	)		75,755
U.S. government-sponsored entity debt securities		8,498		—		(6	)		8,492
Total		194,749		—		(255	)		194,494
Total cash equivalents and available-for-sale securities	$	223,634		—	$	(255	)	$	223,379
December 31, 2016
Cash equivalents:
Money market funds	$	18,992	$	—	$	—		$	18,992
Total		18,992		—		—			18,992
Available-for-sale securities:
Commercial paper securities		23,112		73		—			23,185
Corporate debt securities		10,005		—		(1	)		10,004
U.S. government-sponsored entity debt securities		87,307		3		(25	)		87,285
Total		120,424		76		(26	)		120,474
Total cash equivalents and available-for-sale securities	$	139,416	$	76	$	(26	)	$	139,466

As of December 31, 2017, all of the Company’s investments had maturity dates within two years as of the balance sheet date. The Company had no material realized losses from the sale of available-for-sale securities for the years ended December 31, 2017, 2016 or 2015. Sangamo has the intent and ability to hold its investments for a period of time sufficient to allow for any anticipated recovery in market value. No investments were other-than-temporarily impaired at either December 31, 2017 or 2016.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

NOTE 4 – STOCK-BASED COMPENSATION

The following table shows total stock-based compensation expense recognized in the accompanying consolidated statements of operations (in thousands):


	Year Ended December 31,
	2017		2016		2015
Research and development	$	5,031	$	6,463	$	6,444
General and administrative		4,058		8,594		5,286
Total stock-based compensation expense	$	9,089	$	15,057	$	11,730

As of December 31, 2017, total stock-based compensation expense related to unvested stock options to be recognized in future periods was $16.1 million, which is expected to be expensed over a weighted-average period of 2.79 years. As of December 31, 2017, total stock-based compensation expense related to unvested RSUs to be recognized in future periods was $0.7 million, which is expected to be expensed over a weighted-average period of 1.03 years. There was no capitalized stock-based employee compensation expense as of either December 31, 2017, 2016 or 2015 respectively.

Valuation Assumptions

Employee stock-based compensation expense was determined using the Black-Scholes option valuation model. Option valuation models require the input of subjective assumptions and these assumptions can vary over time.

The Company bases its determination of expected volatility through its assessment of the historical volatility of its common stock. The Company relied on its historical exercise and post-vested termination activity for estimating its expected term for use in determining the fair value of these options.

The weighted-average estimated fair value per share of options granted during 2017, 2016 and 2015 was $4.10, $3.14, and $5.72, respectively, based upon the assumptions used in the Black-Scholes valuation model. The assumptions used for estimating the fair value of the employee stock options are as follows:

	Year Ended December 31,
	2017			2016			2015
Risk-free interest rate	1.81-2.28%			1.13-1.61%			1.46-1.58%
Expected life of option (in years)	5.73-5.83			5.28-5.29			5.25-5.31
Expected dividend yield of stock		0	%		0	%		0	%
Expected volatility	0.71-0.72			0.68-0.70			0.66-0.67

Employees purchased approximately 253,994, 202,711 and 128,181 shares of common stock through the 2010 Employee Stock Purchase Plan at an average exercise price of $3.22, $4.04, and $7.10 per share during 2017, 2016 and 2015, respectively. The weighted-average estimated fair value of shares purchased under the Company’s ESPP during 2017, 2016 and 2015 were $2.37, $2.27 and $4.42, respectively based upon the assumptions used in the Black-Scholes valuation model.

The weighted–average assumptions used for estimating the fair value of the ESPP purchase rights are as follows:

	Year Ended December 31,
	2017			2016			2015
Risk-free interest rate	0.44-0.76%			0.41-0.80%			0.06-0.33%
Expected life of option (in years)	0.5-2.0			0.5-2.0			0.5-2.0
Expected dividend yield of stock		0	%		0	%		0	%
Expected volatility	0.66-0.82			0.71-0.76			0.55-0.70

Major Customers, Partnerships and Strategic Alliances

12 Months Ended

Dec. 31, 2017

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Major Customers, Partnerships and Strategic Alliances

NOTE 5 – MAJOR CUSTOMERS, PARTNERSHIPS AND STRATEGIC ALLIANCES

Collaboration Agreements

Collaboration and License Agreement with Pfizer Inc. in Human Therapeutics

SB-525 Global Collaboration and License Agreement

On May 10, 2017, Sangamo entered into an exclusive, global Collaboration and License Agreement (the “with Pfizer pursuant to which Sangamo and Pfizer established a collaboration for the research, development and commercialization of SB-525, Sangamo’s gene therapy product candidate for hemophilia A, and closely related products (the “hemophilia A Pfizer Agreement”).

Under the hemophilia A Pfizer Agreement, Sangamo will be responsible for conducting the Phase 1/2 clinical trial and certain manufacturing activities for SB-525, while Pfizer will be responsible for subsequent worldwide development, manufacturing, marketing and commercialization of SB-525. Sangamo and Pfizer may also collaborate in the research and development of additional adeno-associated virus (“AAV”)-based gene therapy products for hemophilia A.

Under the hemophilia A Pfizer Agreement, Sangamo received an upfront fee of $70.0 million from Pfizer. In addition, Sangamo is eligible to receive $208.5 million in payments upon the achievement of specified clinical development, intellectual property and regulatory milestones and $266.5 million in payments upon the achievement of specified first commercial sale milestones for SB-525 and potentially other products. The total amount of potential clinical development, intellectual property, regulatory, and first commercial sale milestone payments, assuming the achievement of all specified milestones in the hemophilia A Pfizer Agreement, is $475.0 million, which includes up to $300.0 million for SB-525 and up to $175.0 million for other products that may be developed under the hemophilia A Pfizer Agreement, subject to reduction on account of payments made under certain licenses for third party intellectual property. In addition, Pfizer has agreed to pay Sangamo royalties for each potential licensed product developed under the hemophilia A Pfizer Agreement that are an escalating tiered, double-digit percentage of the annual net sales of such product and are subject to reduction due to patent expiration, entry of biosimilar products to the market and payment made under certain licenses for third party intellectual property. To date, no milestone payments have been received and no products have been approved and therefore no royalty fees have been earned under the hemophilia A Pfizer Agreement. Sangamo in responsible for internal and external research costs as part of the upfront fee and has the ability to request additional reimbursement from Pfizer if certain conditions are met.

Subject to the terms of the hemophilia A Pfizer Agreement, Sangamo granted Pfizer an exclusive, worldwide, royalty-bearing license, with the right to grant sublicenses, to use certain technology controlled by Sangamo for the purpose of developing, manufacturing and commercializing SB-525 and related products. Under the hemophilia A Pfizer Agreement, Pfizer granted Sangamo a non-exclusive, worldwide, royalty free, fully paid license, with the right to grant sublicenses, to use certain manufacturing technology developed under the hemophilia A Pfizer Agreement and controlled by Pfizer to manufacture Sangamo’s products that utilize the AAV delivery system. During a specified period, neither Sangamo nor Pfizer will be permitted to clinically develop or commercialize, outside of the collaboration, certain AAV-based gene therapy products for hemophilia A.

The Company has identified the deliverables within the hemophilia A Pfizer Agreement as a license to the technology and on-going services. The Company concluded that the license is not a separate unit of accounting as it does not have stand-alone value to Pfizer apart from the services to be performed by the Company pursuant to the hemophilia A Pfizer Agreement. As a result, the Company will recognize revenue from the upfront payment on a straight-line basis over a thirty-two month estimated time over which the Company will perform services under the hemophilia A Pfizer Agreement. The recognition period will be reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the period of performance. As of December 31, 2017, the Company had deferred revenue of $53.0 million related to the hemophilia A Pfizer Agreement. During the year ended December 31, 2017 the Company recognized revenue of $17.0 million related to the upfront fee that was received.

C9ORF72 Research Collaboration and License Agreement

On December 28, 2017, Sangamo entered into a Research Collaboration and License Agreement with Pfizer for the development and commercialization of potential gene therapy products that use zinc finger protein transcription factors (“ZFP-TFs”) to treat amyotrophic lateral sclerosis and frontotemporal lobar degeneration, or ALS/ FTLD, linked to mutations of the C9ORF72 gene. Pursuant to this Pfizer Agreement, Sangamo will work together with Pfizer on a research program to identify, characterize and preclinically develop ZFP-TFs that bind to and specifically reduce expression of the mutant form of the C9ORF72 gene (the “ALS/ FTLD Pfizer Agreement”). This agreement was entered into as a separate and distinct agreement apart from the SB-525 Pfizer agreement. The Pfizer C9ORF72 agreement is related to research specific ZFP-TF gene therapy for the C9ORF72 gene, while the SB-525 Pfizer agreement was for the clinical stage development of AAV-based gene therapy products for hemophilia A.

Sangamo has granted Pfizer an exclusive, royalty-bearing, worldwide, sublicensable license under the Company’s relevant patents and know-how to develop, manufacture and commercialize gene therapy products (“Licensed Products”) that use resulting ZFP-TFs that satisfy pre-agreed criteria. During a specified period, neither Sangamo nor Pfizer will be permitted to research, develop, manufacture or commercialize outside of the collaboration any zinc finger proteins that specifically bind to the C9ORF72 gene.

Under the terms of the ALS/ FTLD Pfizer Agreement, Sangamo received a $12.0 million upfront payment from Pfizer. Each party will be responsible for the cost of its performance of the research program. Pfizer will be operationally and financially responsible for subsequent development, manufacturing and commercialization of Licensed Products. Sangamo is eligible to receive up to $60.0 million in development milestone payments from Pfizer if a Licensed Product achieves specified preclinical development, clinical development and first commercial sale milestones, and up to $90.0 million commercial milestone payments if annual worldwide net sales of Licensed Products reach specified levels. In addition, Pfizer will pay royalties to Sangamo that are an escalating tiered, mid- to high-single digit percentage of the annual worldwide net sales of Licensed Products. These royalty payments are subject to reduction due to patent expiration, entry of biosimilar products to the market and payments made under certain licenses for third party intellectual property. Sangamo did not recognize revenue related to this Pfizer agreement as the basic criteria for revenue recognition was not satisfied as of December 31, 2017.

Collaboration and License Agreement with Bioverativ Inc. in Human Therapeutics

In January 2014, the Company entered into a Global Research, Development and Commercialization Collaboration and License Agreement with Biogen (the “Bioverativ Agreement”), and in January 2017 this agreement was assigned by Biogen MA Inc. to Biogen’s blood disorder spin-off, Bioverativ. Pursuant to the Bioverativ Agreement, Sangamo and Bioverativ will collaborate to discover, develop, seek regulatory approval for and commercialize therapeutics based on Sangamo’s zinc finger DNA-binding protein (“ZFP”) technology for beta-thalassemia and sickle cell disease (“SCD”).

Under the Bioverativ Agreement, Sangamo and Bioverativ jointly conduct two research programs: the beta-thalassemia program and the SCD program. For the beta-thalassemia program, Sangamo is responsible for all discovery, research and development activities through the first human clinical trial for the first therapeutic developed under the Bioverativ Agreement for the treatment of beta-thalassemia. For the SCD program, both parties are responsible for research and development activities through the submission of an Investigational New Drug (“IND”) application for a ZFP-based therapeutic intended to treat SCD. For both programs, Bioverativ is responsible for subsequent world-wide clinical development, manufacturing and commercialization of licensed products developed under the Bioverativ Agreement. At the end of specified research terms for each program or under certain specified circumstances, Bioverativ has the right to step in and take over any remaining activities of Sangamo. Furthermore, Sangamo has an option to co-promote in the United States any licensed products to treat beta-thalassemia and SCD developed under the Bioverativ Agreement, and Bioverativ agrees to compensate Sangamo for such co-promotion activities.

Sangamo received an upfront license fee of $20.0 million upon entering into the Bioverativ Agreement. In addition, the Company will also be eligible to receive $115.8 million in payments upon the achievement of specified clinical development and regulatory milestones, as well as $160.5 million in payments upon the achievement of specified sales milestones. Bioverativ reimburses Sangamo for agreed upon costs incurred in connection with research and development activities conducted by Sangamo. In addition, if products are commercialized under the Bioverativ Agreement, Bioverativ will pay Sangamo incremental royalties for each licensed product that are a tiered double-digit percentage of annual net sales of such product. To date, no milestone payments have been received and no products have been approved and therefore no royalty fees have been earned under the Bioverativ Agreement.

In January 2016, the parties agreed on an updated beta-thalassemia development plan and budget using the BCL11A erythroid enhancer target. In November 2016, Sangamo and Bioverativ agreed on an updated beta-thalassemia development plan and budget. As a result of this change, the Company updated the estimated performance period of the upfront license through June 2020, and updated the milestones to be received based on the updated schedule and targets under the Bioverativ Agreement.

All contingent payments under the Bioverativ Agreement, when earned, will be non-refundable and non-creditable. The Company has evaluated the contingent payments under the Bioverativ Agreement based on the authoritative guidance for research and development milestones and determined that certain of these payments meet the definition of a milestone and that all such milestones are evaluated to determine if they are considered substantive milestones. Milestones are considered substantive if they are related to events (i) that can be achieved based in whole or in part on either the Company’s performance or on the occurrence of a specific outcome resulting from the Company’s performance, (ii) for which there was substantive uncertainty at the date the agreement was entered into that the event would be achieved and (iii) that would result in additional payments being due to the Company. Accordingly, consideration received for the achievement of milestones that are determined to be substantive will be recognized as revenue in their entirety in the period when the milestones are achieved and collectability is reasonably assured. Revenue for the achievement of milestones that are not substantive will be recognized over the remaining period of the Bioverativ Agreement, assuming all other applicable revenue recognition criteria have been met.

Subject to the terms of the Bioverativ Agreement, Sangamo has granted Bioverativ an exclusive, royalty-bearing license, with the right to grant sublicenses, to use certain ZFP and other technology controlled by Sangamo for the purpose of researching, developing, manufacturing and commercializing licensed products developed under the Bioverativ Agreement. Sangamo has also granted Bioverativ a non-exclusive, world-wide, royalty free, fully paid license, with the right to grant sublicenses, under Sangamo’s interest in certain other intellectual property developed pursuant to the Bioverativ Agreement.

The Company has identified the deliverables within the arrangement as a license to the technology and on-going research services activities. The Company concluded that the license is not a separate unit of accounting as it does not have stand-alone value to Bioverativ apart from the research services to be performed pursuant to the Bioverativ Agreement. As a result, the Company will recognize revenue from the upfront payment on a straight-line basis over a forty-four month estimated research term as of the November 2016 modification date, during which time the Company will perform research services. The estimated period of performance is reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverables. As of December 31, 2017, the Company had deferred revenue of $4.6 million related to the Bioverativ Agreement.

Revenues recognized under the Bioverativ Agreement for the years ended December 31, 2017, 2016 and 2015 are as follows (in thousands):


	Year Ended December 31,
	2017		2016		2015
Revenue related to Bioverativ Collaboration:
Recognition of upfront fee	$	1,769	$	2,321	$	6,176
Research services		10,489		6,565		7,769
Total	$	12,258	$	8,886	$	13,945

Amended Collaboration and License Agreement with Shire International GmbH in Human Therapeutics

In January 2012, the Company entered into a Collaboration and License Agreement with Shire (the “Shire Agreement ”), pursuant to which the Company and Shire collaborate to research, develop and commercialize human therapeutics and diagnostics for monogenic diseases based on Sangamo’s novel ZFP technology. This agreement was amended on September 1, 2015.

Under the original Shire Agreement, the Company and Shire agreed to develop potential human therapeutic or diagnostic products for seven gene targets. The initial four gene targets selected were blood clotting Factors VII, VIII, IX and X, and products developed for such initial gene targets would be used for treating or diagnosing hemophilia A and B. In June 2012, Shire selected a fifth gene target for the development of a ZFP therapeutic for Huntington’s disease. Shire had the right, subject to certain limitations, to designate two additional gene targets. Pursuant to the Shire Agreement, the Company granted Shire an exclusive, world-wide, royalty-bearing license, with the right to grant sublicenses, to use Sangamo’s ZFP technology for the purpose of developing and commercializing human therapeutic and diagnostic products for the gene targets.

Under the terms of the Shire Agreement, the Company was responsible for all research activities through the submission of an IND or European Clinical Trial Application (CTA), while Shire was responsible for clinical development and commercialization of products generated from the research program from and after the acceptance of an IND or CTA for the product. Shire reimbursed Sangamo for agreed upon internal and external program-related research costs. The Company received an upfront license fee of $13.0 million upon entering into the Shire Agreement in 2012. In 2014, Sangamo recognized a $1.0 million milestone payment related to the hemophilia program.

On September 1, 2015, the Shire Agreement was amended such that Shire agreed to return to Sangamo the exclusive, world-wide rights to gene targets for the development and commercialization of ZFP therapeutics for hemophilia A and B. Shire retains the rights and will continue to develop a ZFP therapeutic for Huntington’s disease. Sangamo will provide certain target feasibility services, and upon Shire’s request, certain research activities according to a research plan as agreed upon by both companies. Such research activities performed by Sangamo will be reimbursed by Shire. Shire’s rights with respect to other targets contemplated in the original agreement revert to Sangamo. Under the revised agreement, each company is responsible for expenses associated with its own programs, and Shire will reimburse Sangamo for any ongoing services provided by Sangamo for Shire’s programs. In 2015, Shire reimbursed Sangamo $3.4 million related to obligations prior to the amendment date which was recognized in revenue as the expense related to those obligations was incurred. Sangamo has granted Shire a right of first negotiation to license the hemophilia A and B programs developed by Sangamo under the amended agreement. Under the amended agreement, Shire does not have any milestone payment obligations with respect to the retained programs, but it is required to pay single digit percentage royalties to Sangamo, up to a specified maximum cap, on the commercial sales of ZFP therapeutic products from such programs. Under the Shire Agreement, Sangamo has full control over, and full responsibility for the costs of, the hemophilia programs returned to us, subject to certain diligence obligations and Shire’s right of first negotiation to obtain a license to such programs under certain circumstances. The Company is required to pay single digit percentage royalties to Shire, up to a specified maximum cap, on commercial sales of ZFP therapeutic products from such returned programs.

The Company has concluded that the license is not a separate unit of accounting as it does not have stand-alone value to Shire apart from the research services to be performed pursuant to the Shire amendment. The Company satisfied the deliverables and research services responsibilities within the amended arrangement which were completed in 2017. As a result, the Company recognized the remaining $2.3 million of deferred revenue from the upfront payment during the year ended December 31, 2017.

Revenues recognized under the Shire Agreement for the years ended December 31, 2017, 2016 and 2015, were as follows (in thousands):


	Year Ended December 31,
	2017		2016		2015
Revenue related to Shire Collaboration:
Recognition of upfront fee	$	2,333	$	2,181	$	2,167
Research services		116		1,096		13,584
Total	$	2,449	$	3,277	$	15,751

Agreement with Sigma-Aldrich Corporation (Sigma) in Laboratory Research Reagents, Transgenic Animal and Commercial Protein Production Cell-line Engineering

In 2007, Sangamo entered into a license agreement with Sigma to provide Sigma with access to Sangamo’s proprietary ZFP technology and the exclusive right to use the technology to develop and commercialize research reagent products and services in the research field, excluding certain agricultural research uses that Sangamo previously licensed to DAS. Sangamo developed laboratory research reagents using its ZFP technology over a three year research services period. Sangamo has since transferred the ZFP manufacturing technology to Sigma.

In October 2009, Sangamo expanded its license agreement with Sigma. In addition to the original terms of the license agreement, Sigma received exclusive rights to develop and distribute ZFP-modified cell lines for commercial production of protein pharmaceuticals and certain ZFP-engineered transgenic animals for commercial applications. Under the terms of the agreement, Sigma made an upfront cash payment of $20.0 million consisting of a $4.9 million purchase of 636,133 shares of Sangamo common stock, valued at $4.9 million, and a $15.1 million upfront license fee. Sangamo is also eligible to receive commercial license fees of $5.0 million based upon a percentage of net sales and sublicensing revenue and thereafter a reduced royalty rate of 10.5% of net sales and sublicensing revenue. In addition, upon the achievement of certain cumulative commercial milestones, Sigma will make milestone payments to Sangamo up to an aggregate of $25.0 million. Sangamo does not have additional ongoing performance obligations under the agreement.

Revenues recognized under the agreement with Sigma for the years ended December 31, 2017, 2016 and 2015, were as follows (in thousands):


	Year Ended December 31,
	2017		2016		2015
Revenue related to Sigma Collaboration:
Royalty revenues	$	452	$	137	$	390
License fee revenues		267		1,140		4,463
Total	$	719	$	1,277	$	4,853

Agreement with Dow AgroSciences in Plant Agriculture

In 2005, Sangamo entered into an exclusive commercial license with Dow AgroSciences, LLC, or DAS, with an initial three year research term. Under this agreement, Sangamo is providing DAS with access to its proprietary ZFP technology and the exclusive right to use the technology to modify the genomes or alter the nucleic acid or protein expression of plant cells, plants, or plant cell cultures. Sangamo has retained rights to use plants or plant-derived products to deliver ZFP TFs or ZFNs into humans or animals for diagnostic, therapeutic or prophylactic purposes. In 2008 DAS exercised its option and obtained a commercial license to sell products incorporating or derived from plant cells generated using the Company’s ZFP technology. The exercise of the option triggered a one-time commercial license fee of $6.0 million, payment of the remaining $2.3 million of the previously agreed upon $4.0 million in research milestones, development and commercialization milestone payments for each product, and royalties on sales of products. Furthermore, DAS has the right to sublicense Sangamo’s ZFP technology to third parties for use in plant cells, plants, or plant cell cultures, and Sangamo will be entitled to 25% of any cash consideration received by DAS under such sublicenses. In December 2010 the Company amended its agreement with DAS to extend the period of reagent manufacturing services and research services through December 31, 2012.

The agreement with DAS also provides for minimum sublicense fees each year due to Sangamo every October, provided the agreement is not terminated by DAS. Annual fees range from $250,000 to $3.0 million and total $25.3 million over 11 years unless terminated at any time by DAS. The Company does not have any performance obligations. In the event of any termination of the agreement, all rights to use the Company’s ZFP technology will revert to Sangamo, and DAS will no longer be permitted to practice Sangamo’s ZFP technology or to develop or, except in limited circumstances, commercialize any products derived from the Company’s ZFP technology.

Revenues under the agreement with DAS were $3.0 million during 2017 and $5.1 million and $3.0 million during 2016 and 2015, respectively.

Acquisition of Ceregene	12 Months Ended
Acquisition of Ceregene	Dec. 31, 2017
Business Combinations [Abstract]
Acquisition of Ceregene	NOTE 6 – ACQUISITION OF CEREGENE In August 2013, Sangamo acquired all the outstanding shares of Ceregene, a privately held biotechnology company focused on the development of AAV gene therapies. The acquired assets included certain intellectual property rights relating to manufacturing of AAV, and toxicology and data from Ceregene’s human clinical trials. The acquisition closed in October 2013 (the Closing Date). The aggregate consideration transferred or transferable by Sangamo to former Ceregene stockholders at closing consisted of 100,000 shares of Sangamo common stock, with an approximate fair value of $1.2 million and a contingent earn-out of $1.5 million on the Closing Date. The $1.8 million fair value of the contingent earn-out liability was reduced to zero in March 2015 upon Sangamo’s decision not to pursue development of Ceregene’s technology as discussed below. Intangible Assets Acquired Intangible assets acquired included In-Process Research and Development (IPR&D), which consisted of Ceregene’s two clinical product candidates, CERE-110 for the treatment of AD and CERE-120 for the treatment of Parkinson’s disease. The Company determined that the combined Closing Date estimated fair values of CERE-110 and CERE-120 was $1.9 million. In the first quarter of 2015, the Company decided to discontinue the CERE-110 and CERE-120 clinical trial programs. As such, the probability of achieving projected revenues and cash flows associated with these programs were adversely affected. The Company does not believe the programs have an alternative future use for itself or other market participants. Accordingly, during the year ended December 31, 2015, the Company recognized a $1.9 million impairment charge related to these assets. Intangible assets also included $1.6 million in goodwill, the excess of the consideration transferred over the fair values assigned to the assets acquired and liabilities assumed. Goodwill represents benefits that Sangamo believes will result from combining its operations with the operations of Ceregene and any intangible assets that do not qualify for separate recognition, as well as any future, yet unidentified products. The Company tests goodwill for impairment on an annual basis or sooner, if deemed necessary. There have been no changes to goodwill since the Closing Date, and no impairment has been recognized.

Property and Equipment

12 Months Ended

Dec. 31, 2017

Property Plant And Equipment [Abstract]

Property and Equipment

NOTE 7 – PROPERTY AND EQUIPMENT

Property and equipment consist of the following (in thousands):

	December 31 ,
	2017			2016
Laboratory equipment	$	7,572		$	6,206
Furniture and fixtures		1,494			636
Leasehold improvements		3,425			1,330
Buildings		3,876			3,876
Total		16,367			12,048
Less accumulated depreciation and amortization		(6,951	)		(5,639	)
Construction in Progress		21,650			148
	$	31,066		$	6,557

Depreciation and amortization expense was $1.5 million in 2017, $1.0 million in 2016 and $1.0 million in 2015. In 2017 the Company capitalized $20.9 million related to the fair value of the Brisbane building and $0.3 million of construction costs in Construction in Progress under the build-to-suit lease guidance (see Note 14). In 2016 the Company capitalized $3.9 million related to the costs of the Richmond construction as a build-to-suit property within property and equipment, net, and recognize a corresponding build-to-suit lease obligation for the same amount. Both buildings will depreciate over the period of their lease, respectively.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2017

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

NOTE 8 – COMMITMENTS AND CONTINGENCIES

Sangamo occupies office and laboratory space under operating leases in Richmond, California. In August 2013, Sangamo amended its lease agreement for our corporate headquarters wherein the lease was extended through August 2019. The Company has three additional properties located in Richmond, CA. This includes two leases, one to occupy approximately 7,700 square feet of research and office space that expires in August 2019, and another to occupy approximately 6,200 square feet of office space that expires in July 2021. Sangamo also has two build-to-suit leases to occupy approximately 41,400 square feet of space in Richmond that expires in December 2021 and approximately 87,700 square feet of space in Brisbane that expires in May 2029. Rent expense related to these lease agreements was $1.1 million, $1.0 million, and $0.9 million for 2017, 2016 and 2015, respectively. Future minimum payments under lease obligations at December 31, 2017 consist of the following (in thousands):


Fiscal Year:
2018	$	1,685
2019		2,925
2020		3,795
2021		3,798
2022		3,335
Thereafter		23,896
Total minimum payments	$	39,434

For 2018, the company is committed to spend $8.8 million for tenant improvements related to the Brisbane build-to-suit lease and $8.7 million as part of our services agreement with Brammer Bio MA, LLC, or Brammer, to provide dedicated capacity to supply our preclinical and clinical programs. The Company also has $5.2 million of license commitments related to its intellectual property.

Contingencies

Sangamo is not party to any material pending legal proceeding. From time to time, we may be involved in legal proceedings arising in the ordinary course of business.

Stockholders' Equity

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

Stockholders' Equity

NOTE 9 – STOCKHOLDERS’ EQUITY

Preferred Stock

The Company has 5,000,000 preferred shares authorized, which may be issued at the discretion of the Company’s Board of Director’s discretion.

Common Stock

On June 26, 2017, Sangamo completed an underwritten public offering of its common stock, in which the Company sold an aggregate of 11.5 million shares of its common stock at a public offering price of $7.25 per share. The net proceeds to Sangamo from the sale of shares in this offering, after deducting underwriting discounts and commissions and other offering expenses, were approximately $78.1 million.

At-the-Market Offering Agreements

On December 7, 2016, we entered into an “at the market” offering agreement with an investment bank, pursuant to which we may issue and sell from time to time up to $75.0 million of our common stock through the bank as the sales agent (“ATM Agreement”). Under the ATM Agreement, if we decide to sell shares, the sales agent will use its commercially reasonable efforts to sell on our behalf all of the shares of common stock requested to be sold by us. Sales of the common stock, if any, will be made at market prices by any method that is deemed to be an “at the market offering” as defined in Rule 415 under the Securities Act, as amended, including sales made directly on The Nasdaq Global Market and any other trading market for the common stock, and sales to or through a market maker other than on an exchange. In addition, with our prior written consent, the sales agent may also sell our common stock in negotiated transactions.

On May 26, 2017, the Company entered into an Amended and Restated At-the-Market Offering Program Sales Agreement (the “2017 ATM Agreement”) with an investment bank pursuant to which the Company may issue and sell from time to time after the date of the 2017 ATM Agreement, shares of its common stock having an aggregate offering price of up to $75.0 million through the investment bank acting as the Company’s sales agent. Under the 2017 ATM Agreement, if the Company decides to sell shares, the Company will notify the sales agent, and the sales agent will use its commercially reasonable efforts to sell on the Company’s behalf all of the shares of common stock requested to be sold. Sales of the Company’s common stock, if any, will be made at market prices by any method that is deemed to be an “at the market offering” as defined in Rule 415 under the Securities Act, as amended, including sales made directly on The NASDAQ Global Select Market and sales to or through a market maker other than on an exchange. In addition, with the Company’s prior written consent, the sales agent may also sell shares of its common stock in negotiated transactions under the 2017 ATM Agreement. During the three months ended March 31, 2017, the Company issued a total of 871,149 shares of its common stock under the original At-the-Market Offering Program Sales Agreement entered into with the sales agent in December 2016, and received net proceeds of $3.4 million, after deducting offering expenses, including $0.1 million of commission paid to the sales agent. These shares were inadvertently sold under a registration statement filed with the SEC that had in fact expired prior to the time the shares were sold. Consequently, the Company may be subject to claims for rescission by purchasers who purchased shares of common stock under the ATM Agreement in March 2017. Under Section 12(a)(1) of the Securities Act, a purchaser of security in a transaction made in violation of Section 5 of the Securities Act may obtain recovery of the consideration paid in connection with its purchase, plus statutory interest, or, if it had already sold the shares, recover damages resulting from its purchase. While the Company believes it is unlikely that a successful claim will be asserted against the Company by any purchasers who purchased shares of common stock under the ATM Agreement in March 2017, the Company cannot guarantee that no such legal claims will be asserted against the Company by any purchasers. In addition, the Company could become subject to enforcement actions and/or penalties and fines by federal authorities, and the Company is unable to predict the likelihood of any such enforcement actions being brought, or the amount of any such potential penalties or fines.

Stock Incentive Plan

In April 2013 Sangamo’s Board of Directors adopted, subject to stockholder approval, the Company’s 2013 Stock Incentive Plan (the 2013 Plan) as the successor to the Company’s 2004 Stock Incentive Plan (the 2004 Plan). At the Annual Meeting of Stockholders held on June 12, 2013, the 2013 Plan was approved by the Company’s stockholders and became effective. In connection with the approval by stockholders of the 2013 Plan, outstanding awards under the 2004 Plan were transferred to the 2013 Plan. The 2004 Plan was terminated and no further awards will be made pursuant to the 2004 Plan.

Under the 2013 Plan, the exercise price per share of options granted will generally not be less than 100 percent of the fair value per share of common stock on the grant date, and the option term will not exceed ten years. If the person to whom the option is granted is a 10 percent stockholder, and the option granted qualifies as an Incentive Stock Option Grant, then the exercise price per share will not be less than 110 percent of the fair value per share of common stock on the grant date, and the option term will not exceed five years. Options granted under the 2013 Plan generally vest over four years at a rate of 25 percent one year from the grant date and one thirty-sixth per month thereafter and expire ten years after the grant, or earlier upon employment termination. Certain options previously granted under the 2004 Plan to the Company’s non-employee directors are structured so that they may be exercised prior to vesting, with the related shares subject to Sangamo’s right to repurchase any shares that have not vested pursuant to the vesting schedule in effect for such award at the exercise price paid if the option holder’s board service terminates. Approximately 14.1 million shares were initially reserved for issuance under the 2013 Plan, including 9.7 million shares of common stock subject to outstanding awards previously granted under the 2004 Plan that were transferred to the 2013 Plan, and an additional 4.4 million shares of common stock.

The number of shares of common stock reserved for issuance under the 2013 Plan will be reduced: (i) on a 1-for-1 basis for each share of common stock subject to a stock option or stock appreciation right granted under the plan, (ii) on a 1-for-1 basis for each share of common stock issued pursuant to a full value award granted under the plan prior to the plan effective date, and (iii) by a fixed ratio of 1.33 shares of common stock for each share of common stock issued pursuant to a full-value award granted under the plan on or after the plan effective date.

Shares subject to any outstanding options or other awards under the 2013 Plan that expire or otherwise terminate prior to the issuance of the shares subject to those options or awards will be available for subsequent issuance under the 2013 Plan. Any unvested shares issued under the 2013 Plan that the Company subsequently purchases, pursuant to repurchase rights under the 2013 Plan, will be added back to the number of shares reserved for issuance under the 2013 Plan on a 1-for-1 basis or a 1.33-for-1 basis (depending on the ratio at which the share reserve was debited for the original award) and will accordingly be available for subsequent issuance in accordance with the terms of the plan.

In June 2015 Sangamo’s stockholders were asked to vote to approve the amendment and restatement of our 2013 Stock Incentive Plan in order to increase the number of shares in our common stock reserved for issuance over the term of the 2013 Plan by 5,300,000 shares. At the Annual Meeting of Stockholders held on June 22, 2015, the amendment and restatement of our 2013 Stock Incentive Plan was approved by the Company’s stockholders and became effective.

On November 10, 2017, the Compensation committee of the Company’s Board of Directors approved the amendment and restatement of the Company’s Amended and Restated 2013 Stock Incentive Plan, to reserve an additional one million shares of the Company’s common stock to be used exclusively for grants of awards to individuals who were not previously employees or non-employee directors of the Company (or following a bona fide period of non-employment with the Company), as an inducement material to each such individual’s entry into employment with us within the meaning of Rule 5635(c)(4) of the NASDAQ Listing Rules, or Rule 5635(c)(4). The 2013 Plan was amended and restated by the Compensation Committee without stockholder approval pursuant to Rule 5635(c)(4).

Employee Stock Purchase Plan

Sangamo’s 2010 Employee Stock Purchase Plan (“Purchase Plan”), which supersedes the Company’s 2000 Employee Stock Purchase Plan, provides a total reserve of 2,100,000 shares of common stock for issuance under the Purchase Plan. Eligible employees may purchase common stock at 85 percent of the lesser of the fair market value of Sangamo’s common stock on the first day of the applicable two-year offering period or the last day of the applicable six-month purchase period.

Stock Option Activity

A summary of Sangamo’s stock option activity is as follows:

				Weighted-
				Average		Weighted Average		Aggregate
	Number of			Exercise per		Remaining		Intrinsic
	Shares			Share Price		Contractual Term		Value
						(In years)		(In thousands)
Options outstanding at December 31, 2016		9,256,506		$	8.31
Options granted		3,091,125		$	6.48
Options exercised		(2,030,815	)	$	7.76
Options canceled		(2,029,360	)	$	8.28
Options outstanding at December 31, 2017		8,287,456		$	7.77		6.69	$	71,658
Options vested and expected to vest at December 31, 2017		8,287,456		$	7.77		6.69	$	71,658
Options exercisable at December 31, 2017		3,881,078		$	8.99		4.13	$	28,864

Newly created shares are issued upon exercises of options. There were no shares subject to Sangamo’s right of repurchase as of December 31, 2017. The intrinsic value of options exercised was $12.3 million, $0.1 million and $6.4 million during 2017, 2016 and 2015, respectively.

At December 31, 2017, the aggregate intrinsic values of outstanding and exercisable options were $71.7 million and $28.9 million, respectively. The aggregate intrinsic value of options vested and expected to vest as of December 31, 2017, 2016 and 2015 was $71.7 million, $0.0 million and $14.0 million, respectively.

The following table summarizes information with respect to stock options outstanding at December 31, 2017:

	Options Outstanding and Exercisable				Options Exercisable
	Number of				Number of
	Shares of				Shares of
	common stock		Weighted Average		common stock
	subject to		Remaining		subject to		Weighted Average
Range of Exercise Price	options		Contractual Life		options		Exercise Price
			(In years)
$2.55 – $3.45		612,318		7.92		214,920	$	3.13
$3.50 – $3.50		1,527,625		9.07		—	$	—
$3.55 – $5.41		1,212,567		5.24		672,930	$	5.34
$5.42 – $7.07		1,501,051		5.53		967,506	$	6.11
$7.20 – $9.41		1,199,546		7.17		551,162	$	9.06
$9.45 – $13.35		885,599		5.52		659,946	$	11.92
$13.54 – $15.00		1,148,250		6.26		668,752	$	14.07
$15.11 – $18.26		178,000		7.31		124,561	$	16.41
$19.51 – $19.51		10,000		6.14		9,583	$	19.51
$19.80 – $19.80		12,500		6.23		11,718	$	19.80
		8,287,456		6.69		3,881,078	$	8.99

Restricted Stock Units

During 2017, 2016 and 2015, the Company awarded 12,600, 60,000, and 446,000 Restricted Stock Units (RSUs), respectively. The RSUs awarded in 2017, 2016 and 2015 had an average grant date fair value per award of $15.85, $5.16 and $9.45, respectively. These awards generally vest as follows: one-third of the award will vest in a series of three successive equal annual installments. The aggregate fair value of RSUs vested during 2017, 2016 and 2015 was $1.2 million, $4.8 million and $4.1 million, respectively.

A summary of Sangamo’s RSU activity is as follows:

	Number			Weighted Average
	of			Remaining		Aggregate Intrinsic
	Shares			Contractual Term		Value
				(In years)		(In thousands)
RSUs outstanding at December 31, 2016		321,816
RSUs awarded		12,600
RSUs released		(112,917	)
RSUs forfeited		(141,327	)
RSUs outstanding at December 31, 2017		80,172			0.90	$	1,315
RSUs vested and expected to vest at December 31, 2017		80,172			0.90	$	1,315

RSUs that vested in 2017, 2016 and 2015 were net-share settled such that the Company withheld shares with value equivalent to the employees’ minimum statutory obligation for the applicable income and other employment taxes, and remitted the cash to the appropriate taxing authorities. The total shares withheld were approximately 42,243, 165,181, and 172,807 for 2017, 2016 and 2015, respectively and were based on the value of the RSUs on their respective issuance dates as determined by the Company’s closing stock price. Total payments for the employees’ tax obligations to taxing authorities were $0.7 million, $0.8 million and $1.5 million in 2017, 2016 and 2015, respectively and are reflected as a financing activity within the accompanying consolidated statements of cash flows. These net-share settlements had the effect of share repurchases by the Company as they reduced and retired the number of shares that would have otherwise been issued as a result of the vesting and did not represent an expense to the Company.

As of December 31, 2017, there were 3,601,633 shares reserved for future awards under the Company’s 2013 Plan and 835,674 shares of common stock reserved for future issuance under the Purchase Plan.

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Income Taxes

NOTE 10 – INCOME TAXES

The benefit for income taxes consisted of the following (in thousands):

	Year Ended December 31,
	2017		2016			2015
Benefit for income taxes:
Current:
Federal	$	—	$	—		$	—
State		—		—			—
Subtotal		—		—			—
Deferred:
Federal	$	—	$	(12	)	$	(5,563	)
State		—		(2	)		(159	)
Subtotal		—		(14	)		(5,722	)
Income tax benefit	$	—	$	(14	)	$	(5,722	)

The difference between the benefit for income taxes and the amount computed by applying the federal statutory income tax rate (34%) to loss before taxes is explained as follows (in thousands):

	Year Ended December 31,
	2017			2016			2015
Tax at federal statutory rate	$	(18,553	)	$	(24,369	)	$	(15,785	)
State taxes, net		795			(747	)		4,840
Federal Rate Change		53,045			—			—
Non-deductible stock compensation		2,120			2,781			1,085
Research credits		(869	)		(1,424	)		(814	)
Change in valuation allowance		(36,575	)		23,773			5,043
Other		37			(28	)		(91	)
Income tax benefit	$	—		$	(14	)	$	(5,722	)

Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s deferred tax assets are as follows (in thousands):

	December 31 ,
	2017		2016
Assets:
Deferred tax assets:
Net operating loss carryforwards	$	91,308	$	114,222
Research and development tax credit carryforwards		15,147		12,518
Stock-based compensation		3,168		8,565
Deferred revenue		934		2,918
Other		2,276		3,492
Total deferred tax asset		112,833		141,715
Valuation allowance		112,833		141,715
Net deferred tax assets	$	—	$	—
Liabilities:
Net deferred tax liability related to intangible assets		—		—
Total deferred tax liability	$	—	$	—

In October 2013, we acquired Ceregene. The Company recorded goodwill and intangible assets as part of accounting for the acquisition of Ceregene. A portion of the intangible assets acquired were for the use in a particular research and development project IPR&D and are considered indefinite-lived assets with no tax basis. In 2015, the Company impaired these intangible assets and reversed the corresponding deferred tax liability.

In 2015 the Company received a $14.5 million Section 16(b) disgorgement settlement that was recognized as additional paid-in capital. The disgorgement settlement was recognized net of taxes of $9.5 million, which resulted in an income tax benefit of $5.0 million being recognized in the accompanying consolidated statements of operations for the year ended December 31, 2015.

The changes in the fair value of the unrealized gain/loss on securities investment are recorded as a component of accumulated other comprehensive income, net of a provision for income taxes.

A valuation allowance is recorded when it is more likely than not that all or some portion of the deferred income tax assets will not be realized. We regularly assess the need for a valuation allowance against our deferred income tax assets by considering both positive and negative evidence related to whether it is more likely than not that our deferred income tax assets will be realized. In evaluating our ability to recover our deferred income tax assets within the jurisdiction from which they arise, we consider all available positive and negative evidence, including scheduled reversals of deferred income tax liabilities, projected future taxable income, tax-planning strategies, and results of recent operations. Accordingly, based upon the Company’s analysis of these factors the net deferred tax assets have been fully offset by a valuation allowance. The valuation allowance (decreased) increased by $(28.9) million, $23.8 million and $5.0 million for the years ended December 31, 2017, 2016 and 2015, respectively. As of December 31, 2017, Sangamo had net operating loss carryforwards for federal and state income tax purposes of approximately $475 million and $142 million, respectively. If not utilized, the net federal and state operating loss carryforwards will expire in 2018 and 2017, respectively. The Company also has federal and state research tax credit carryforwards of $10.8 million and $11.8 million, respectively. The federal research credits will begin to expire in 2018 while the state research credits have no expiration date. Utilization of the Company’s net operating loss carryforwards and research tax credit carryforwards may be subject to substantial annual limitations due to the ownership change limitations provided by the Internal Revenue Code and similar state provisions. The annual limitation could result in the expiration of the net operating loss carryforwards and research tax credit carryforwards before utilization.

On December 22, 2017, President Trump signed the Tax Cuts and Jobs Act ("Tax Reform") into legislation. The Tax Reform makes significant changes to the US corporate income tax law including, but not limited to, (1) reducing the U.S. federal corporate tax rate to 21% from 35% and (2) requiring a one-time mandatory transition tax on previously deferred foreign earnings of US subsidiaries. Under ASC 740, the effects of changes in tax rates and laws are recognized in the period in which the new legislation is enacted. In the case of US federal income taxes, the enactment date is the date the bill becomes law. With respect to this legislation, we expect no financial statement impact due to the Company's valuation allowance. The Company performed a re-measurement of deferred tax assets and liabilities as a result of the decrease in the corporate Federal income tax rate from 35% to 21%. In addition to the reduction of U.S. federal corporate tax rate, the Company has also considered the impact of the foreign transition tax for which it has estimated that it would not need to accrue any amounts.

In December 2017, the Securities and Exchange Commission staff issued Staff Accounting Bulletin No.118 (SAB 118) to provide guidance on the application of the Tax Reform when a company does not have the necessary information available, prepared, or analyzed in reasonable to detail to reflect the effects of the Tax Reform. SAB 118 provides guidance for companies under the three scenarios (1) measurement of certain income tax effects is complete, (2) measurement of certain income tax effect can be reasonably estimated, and (3) measurement of certain income tax effects cannot be reasonably estimated. Companies are to complete the accounting under ASC 740 in regards to the Tax Reform within a measurement period that does not extend one year from the date of enactment (i.e., December 22, 2018). In accordance with SAB 118, companies must reflect the tax effects of the Tax Reform for which the accounting under 740 is complete. If certain income tax effect can be reasonably estimated, then the companies must report provisional amounts in the reporting period in which the companies can determine the reasonable estimate during the measurement period. In the case that certain income tax effects cannot be reasonably estimated, companies do not have to report effects of the Tax Reform. However, they should continue to apply ASC 740 based on the rules before the enactment of the Tax Reform and report any income tax effects in the first reporting period in which reasonable estimates become available.

We expect the new law to significantly reduce our tax rate in future periods, and our tax footnote reflects the effects of a Federal tax rate reduction net of our valuation allowance, which resulted in a net overall reduction of $0.

The final transition impacts of the Tax Act may differ from the above estimate, possibly materially, due to, among other things, changes in interpretations of the Tax Act, any legislative action to address questions that arise because of the Tax Act, any changes in accounting standards for income taxes or related interpretations in response to the Tax Act, or any updates or changes to estimates the company has utilized to calculate the transition impacts, including impacts from changes to current year earnings estimates and foreign exchange rates of foreign subsidiaries. In accordance with SAB 118, the Company is allowed a measurement period of up to one year after the enactment date of the Tax Act to finalize the recording of the related tax impacts. We currently anticipate finalizing and recording any resulting adjustments by year ending December 31, 2018.

The Company files federal and state income tax returns with varying statutes of limitations. The tax years from 2002 forward remain open to examination due to the carryover of net operating losses or tax credits. The Company also files a UK income tax return, and the tax years from 2008 and thereafter remain open to examination.

The Company’s practice is to recognize interest and/or penalties related to income tax matters in income tax expense. As of December 31, 2017, the Company had no accrued interest and/or penalties. The unrecognized tax benefits may change during the next year for items that arise in the ordinary course of business. In the event that any unrecognized tax benefits are recognized, the effective tax rate will not be affected.

The following table summarizes the activity related to the Company’s unrecognized tax benefits (in thousands):

	December 31,
	2017			2016			2015
Beginning balance	$	5,045		$	8,330		$	3,438
Additions based on tax positions related to the current year		622			1,023			557
Additions for tax positions of prior years		(8	)		27			4,335
Reductions for tax positions of prior years		—			(4,335	)		—
Ending balance	$	5,659		$	5,045		$	8,330

Accounts Payable and Accrued Liabilities

12 Months Ended

Dec. 31, 2017

Payables And Accruals [Abstract]

Accounts Payable and Accrued Liabilities

NOTE 11 – ACCOUNTS PAYABLE AND ACCRUED LIABILITIES

Accounts payable and accrued liabilities consist of the following (in thousands):

	December 31 ,
	2017		2016
Accounts payable	$	16	$	2,580
Accrued research and development expenses		7,898		2,887
Accrued professional fees		1,318		270
Deferred rent		417		498
Other		1,386		26
Total accounts payable and accrued liabilities	$	11,035	$	6,261

Employee Benefit Plan	12 Months Ended
Employee Benefit Plan	Dec. 31, 2017
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plan	NOTE 12 – EMPLOYEE BENEFIT PLAN The Company sponsors a defined-contribution savings plan under Section 401(k) of the Internal Revenue Code covering all full-time employees (Sangamo 401(k) Plan). The Sangamo 401(k) Plan is intended to qualify under Section 401 of the Internal Revenue Code. The Company matched employee contributions equal to 50% for the first 8% in 2017 and 6% in both 2016 and 2015, respectively, up to a limit of $4,000 in 2017 and $3,000 in both 2016 and 2015, respectively. Matching funds are fully vested when contributed. Contributions to the Sangamo 401(k) Plan by the Company were $0.5 million, $0.3 million, and $0.3 million for the years ended December 31, 2017, 2016 and 2015, respectively.

Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Data (Unaudited)

NOTE 13 – QUARTERLY FINANCIAL DATA (UNAUDITED)

The following table sets forth certain unaudited quarterly financial data for the eight quarters ended December 31, 2016. The unaudited information set forth below has been prepared on the same basis as the audited information contained herein and includes all adjustments necessary to present fairly the information set forth. The operating results for any quarter are not indicative of results for any future period. All data is in thousands except per share data.

	2017												2016
	Q1			Q2			Q3			Q4			Q1			Q2			Q3			Q4
Revenues	$	3,425		$	8,253		$	11,812		$	13,077		$	3,942		$	3,702		$	2,823		$	8,922
Expenses	$	20,217		$	21,021		$	24,847		$	26,843		$	20,623		$	30,544		$	22,029		$	18,752
Net loss	$	(16,632	)	$	(12,491	)	$	(12,354	)	$	(13,091	)	$	(16,494	)	$	(26,575	)	$	(18,965	)	$	(9,624	)
Net loss per share	$	(0.23	)	$	(0.17	)	$	(0.15	)	$	(0.15	)	$	(0.23	)	$	(0.38	)	$	(0.27	)	$	(0.14	)

Build-to-Suit Lease	12 Months Ended
Build-to-Suit Lease	Dec. 31, 2017
Leases Operating [Abstract]
Build-to-Suit Lease	NOTE 14 – BUILD-TO-SUIT LEASE Brisbane Build-to-Suit Lease In November 2017, the Company entered into a long-term property lease which includes construction by the lessor of a building with approximately 87,700 square feet of space, in Brisbane, California. Substantial completion of the building is estimated to occur in the last quarter of 2018. The lease agreement expires in May 2029, approximately ten years after substantial completion of the building. A letter of credit for $3.5 million was established as the deposit and is classified within other noncurrent assets in the financial statements. The Company has two options to extend the lease term for up to a combined additional ten years. The Company is deemed, for accounting purposes only, to be the owner of the entire project including the building shell, even though it is not the legal owner as a result of the cold shell condition of the building and involvement in the construction process. In connection with the Company’s accounting for this transaction, the Company capitalized the costs of construction as a build-to-suit property within property and equipment, net, and recognize a corresponding build-to-suit lease obligation, including interest. Fair value of the building was estimated at $20.9 million using comparable market prices per square foot for similar space for public real estate transactions in the surrounding area and is considered a Level 2 fair value measurement. As of December 31, 2017, $21.2 million was capitalized with a corresponding build-to-suit lease obligation recognized related to this lease for the building and construction costs. Point Pinole Build-to-Suit Lease In December 2015, the Company entered into a long-term property lease which includes construction by the lessor of a building with approximately 41,400 square feet of space, in Richmond, California. Substantial completion of the building was accomplished in December 2016 at which time the lease commenced. The lease agreement expires in December 2021, five years after substantial completion of the building. The Company has two options to extend the lease term for up to a combined additional ten years. The Company is deemed, for accounting purposes only, to be the owner of the entire project including the building shell, even though it is not the legal owner. In connection with the Company’s accounting for this transaction, the Company capitalized the costs of construction as a build-to-suit property within property and equipment, net, and recognize a corresponding build-to-suit lease obligation for the same amount. As of December 31, 2016, $3.9 million of costs were capitalized in buildings with a corresponding build-to-suit lease obligation recognized related to this lease. Construction has completed on the facility and as such a portion of the monthly lease payment is allocated to land rent and recorded as an operating lease expense and the non-interest portion of the amortized lease payments to the landlord related to the rent of the building is applied to reduce the build-to-suit lease obligation.

Claims Settlement	12 Months Ended
Claims Settlement	Dec. 31, 2017
Claims Settlement Disclosure [Abstract]
Claims Settlement	NOTE 15 – CLAIMS SETTLEMENT In September 2015, the Company received $14.5 million as a settlement with certain institutional investors that were beneficial owners of Sangamo’s common stock related to the disgorgement of short-swing profits pursuant to Section 16(b) of the Securities Exchange Act of 1934, as amended. The settlement of $9.5 million, net of a $5.0 million income tax benefit and certain expenses, was recognized as additional paid-in capital.

Subsequent Event	12 Months Ended
Subsequent Event	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Event	NOTE 16 – SUBSEQUENT EVENT In February 2018, the Company entered into a Collaboration and License Agreement with Kite Pharma, Inc. (“Kite”), a wholly-owned subsidiary of Gilead Sciences, Inc. (“Gilead”), for the research, development and commercialization of potential engineered cell therapies for cancer. The Company will work together with Kite on a research program under which the Company ZFNs and AAVs to disrupt and insert certain genes in T cells and NK cells, including the insertion of genes that encode CARs, T-cell receptors (“TCRs”) and NK cell receptors (“NKRs”) directed to mutually agreed targets. Kite will be responsible for all clinical development and commercialization of any resulting products. Except for confidentiality obligations and certain representations, warranties and covenants, which are effective upon execution, the effectiveness of the Kite agreement is subject to the expiration or termination of all applicable waiting periods under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended and other customary closing conditions. Under the terms of the Kite agreement, the Company will, upon the effectiveness of the Kite agreement, receive a $150 million upfront payment from Kite. Kite will reimburse the Company’s direct costs to conduct the joint research program under the Kite agreement, and Kite will be operationally and financially responsible for all subsequent development, manufacturing and commercialization of licensed products. The Company is also eligible to receive contingent development- and sales-based milestone payments that could total up to $3.01 billion if all of the specified milestones set forth in the Kite agreement are achieved. Of this amount, approximately $1.26 billion relates to the achievement of specified research, clinical development, regulatory and first commercial sale milestones, and approximately $1.75 billion relates to the achievement of specified sales-based milestones if annual worldwide net sales of licensed products reach specified levels. Each development- and sales-based milestone payment is payable (i) only once for each licensed product, regardless of the number of times that the associated milestone event is achieved by such licensed product, and (ii) only for the first ten times that the associated milestone event is achieved, regardless of the number of licensed products that may achieve such milestone event. In addition, the Company will be entitled to receive escalating, tiered royalty payments with a percentage in the mid-single digits based on potential future annual worldwide net sales of licensed products. These royalty payments will be subject to reduction due to patent expiration, entry of biosimilar products to the market and payments made under certain licenses for third-party intellectual property. At this time the Company is assessing the accounting impact of the agreement.

Organization and Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Basis of Presentation

The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. The consolidated financial statements include the accounts of Sangamo and its wholly-owned subsidiaries, Ceregene and Gendaq Limited, after elimination of all intercompany balances and transactions.

Business Combinations

Cash and Cash Equivalents

Marketable Securities

Fair Value Measurements

Property and Equipment

Use of Estimates

The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the financial statements and the accompanying notes. On an ongoing basis, management evaluates its estimates, including critical accounting policies or estimates related to revenue recognition, clinical trial accruals, and stock-based compensation. Estimates are based on historical experience and on various other market specific and other relevant assumptions that the Company believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results could differ from those estimates. During the fourth quarter of 2016, we revised our estimated performance period under the Bioverativ license agreement from June 2019 to June 2020, which also extended the recognition period of the related up-front payment we received upon entering this agreement (See Note 5). This change decreased revenues by $4.3 million and increased net loss and net loss per share by $0.06 for the year ended December 31, 2016.

Revenue Recognition

Multiple Element Arrangements after the adoption of ASU 2009-13. ASU 2009-13 amended the accounting standards for certain multiple element revenue arrangements to:

•

eliminate the use of the residual method and require an entity to allocate arrangement consideration using the relative selling price method.

Research and Development Expenses

Stock-Based Compensation

Indefinite-Lived Intangible Assets

In-Process Research and Development

Goodwill

Contingent Consideration Liability

Income Taxes

Net Loss Per Share

Segments

Recent Accounting Pronouncements

Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Summary of Fair Value Measurements of Cash Equivalents, Available-for-Sale Securities and Contingent Consideration Liability

	December 31, 2017
	Fair Value Measurements
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	24,290	$	24,290	$	—	$	—
Commercial paper securities		4,595		—		4,595		—
Total		28,885		24,290		4,595		—
Marketable securities:
Commercial paper securities		110,247		—		110,247		—
Corporate debt securities		75,755		—		75,755		—
U.S. government-sponsored entity debt securities		8,492		—		8,492		—
Total		194,494		—		194,494		—
Total cash equivalents and marketable securities	$	223,379	$	24,290	$	199,089		—

	December 31, 2016
	Fair Value Measurements
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	18,992	$	18,992	$	—	$	—
Total		18,992		18,992		—		—
Marketable securities:
Commercial paper securities		23,185		—		23,185		—
Corporate debt securities		10,004		—		10,004		—
U.S. government-sponsored entity debt securities		87,285		—		87,285		—
Total		120,474		—		120,474		—
Total cash equivalents and marketable securities	$	139,466	$	18,992	$	120,474	$	—

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2017

Investments Debt And Equity Securities [Abstract]

Summary of Cash Equivalents and Available-for-Sale Securities

The table below summarizes the Company’s cash equivalents and available-for-sale securities (in thousands):

			Gross		Gross
	Amortized		Unrealized		Unrealized			Estimated
	Cost		Gains		(Losses)			Fair Value
December 31, 2017
Cash equivalents:
Money market funds	$	24,290	$	—	$	—		$	24,290
Commercial paper securities		4,595		—		—			4,595
Total		28,885		—		—			28,885
Available-for-sale securities:
Commercial paper securities		110,365		—		(118	)		110,247
Corporate debt securities		75,886		—		(131	)		75,755
U.S. government-sponsored entity debt securities		8,498		—		(6	)		8,492
Total		194,749		—		(255	)		194,494
Total cash equivalents and available-for-sale securities	$	223,634		—	$	(255	)	$	223,379
December 31, 2016
Cash equivalents:
Money market funds	$	18,992	$	—	$	—		$	18,992
Total		18,992		—		—			18,992
Available-for-sale securities:
Commercial paper securities		23,112		73		—			23,185
Corporate debt securities		10,005		—		(1	)		10,004
U.S. government-sponsored entity debt securities		87,307		3		(25	)		87,285
Total		120,424		76		(26	)		120,474
Total cash equivalents and available-for-sale securities	$	139,416	$	76	$	(26	)	$	139,466

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation Expense

The following table shows total stock-based compensation expense recognized in the accompanying consolidated statements of operations (in thousands):


	Year Ended December 31,
	2017		2016		2015
Research and development	$	5,031	$	6,463	$	6,444
General and administrative		4,058		8,594		5,286
Total stock-based compensation expense	$	9,089	$	15,057	$	11,730

Assumptions Used for Estimating Fair Value of Employee Stock Options

The assumptions used for estimating the fair value of the employee stock options are as follows:

	Year Ended December 31,
	2017			2016			2015
Risk-free interest rate	1.81-2.28%			1.13-1.61%			1.46-1.58%
Expected life of option (in years)	5.73-5.83			5.28-5.29			5.25-5.31
Expected dividend yield of stock		0	%		0	%		0	%
Expected volatility	0.71-0.72			0.68-0.70			0.66-0.67

Weighted-Average Assumptions Used for Estimating Fair Value of ESPP Purchase Rights

The weighted–average assumptions used for estimating the fair value of the ESPP purchase rights are as follows:

	Year Ended December 31,
	2017			2016			2015
Risk-free interest rate	0.44-0.76%			0.41-0.80%			0.06-0.33%
Expected life of option (in years)	0.5-2.0			0.5-2.0			0.5-2.0
Expected dividend yield of stock		0	%		0	%		0	%
Expected volatility	0.66-0.82			0.71-0.76			0.55-0.70

Major Customers, Partnerships and Strategic Alliances (Tables)

12 Months Ended

Dec. 31, 2017

Bioverativ Inc [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenues Recognized under Agreement

Revenues recognized under the Bioverativ Agreement for the years ended December 31, 2017, 2016 and 2015 are as follows (in thousands):


	Year Ended December 31,
	2017		2016		2015
Revenue related to Bioverativ Collaboration:
Recognition of upfront fee	$	1,769	$	2,321	$	6,176
Research services		10,489		6,565		7,769
Total	$	12,258	$	8,886	$	13,945

Shire AG [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenues Recognized under Agreement

Revenues recognized under the Shire Agreement for the years ended December 31, 2017, 2016 and 2015, were as follows (in thousands):


	Year Ended December 31,
	2017		2016		2015
Revenue related to Shire Collaboration:
Recognition of upfront fee	$	2,333	$	2,181	$	2,167
Research services		116		1,096		13,584
Total	$	2,449	$	3,277	$	15,751

Sigma-Aldrich Corporation [Member]

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenues Recognized under Agreement

Revenues recognized under the agreement with Sigma for the years ended December 31, 2017, 2016 and 2015, were as follows (in thousands):


	Year Ended December 31,
	2017		2016		2015
Revenue related to Sigma Collaboration:
Royalty revenues	$	452	$	137	$	390
License fee revenues		267		1,140		4,463
Total	$	719	$	1,277	$	4,853

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

Property Plant And Equipment [Abstract]

Summary of Property and Equipment

Property and equipment consist of the following (in thousands):

	December 31 ,
	2017			2016
Laboratory equipment	$	7,572		$	6,206
Furniture and fixtures		1,494			636
Leasehold improvements		3,425			1,330
Buildings		3,876			3,876
Total		16,367			12,048
Less accumulated depreciation and amortization		(6,951	)		(5,639	)
Construction in Progress		21,650			148
	$	31,066		$	6,557

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments And Contingencies Disclosure [Abstract]

Summary of Future Minimum Payments under Contractual Obligations

Future minimum payments under lease obligations at December 31, 2017 consist of the following (in thousands):


Fiscal Year:
2018	$	1,685
2019		2,925
2020		3,795
2021		3,798
2022		3,335
Thereafter		23,896
Total minimum payments	$	39,434

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

Summary of Stock Option Activity

A summary of Sangamo’s stock option activity is as follows:

				Weighted-
				Average		Weighted Average		Aggregate
	Number of			Exercise per		Remaining		Intrinsic
	Shares			Share Price		Contractual Term		Value
						(In years)		(In thousands)
Options outstanding at December 31, 2016		9,256,506		$	8.31
Options granted		3,091,125		$	6.48
Options exercised		(2,030,815	)	$	7.76
Options canceled		(2,029,360	)	$	8.28
Options outstanding at December 31, 2017		8,287,456		$	7.77		6.69	$	71,658
Options vested and expected to vest at December 31, 2017		8,287,456		$	7.77		6.69	$	71,658
Options exercisable at December 31, 2017		3,881,078		$	8.99		4.13	$	28,864

Summary of Stock Options Outstanding

The following table summarizes information with respect to stock options outstanding at December 31, 2017:

	Options Outstanding and Exercisable				Options Exercisable
	Number of				Number of
	Shares of				Shares of
	common stock		Weighted Average		common stock
	subject to		Remaining		subject to		Weighted Average
Range of Exercise Price	options		Contractual Life		options		Exercise Price
			(In years)
$2.55 – $3.45		612,318		7.92		214,920	$	3.13
$3.50 – $3.50		1,527,625		9.07		—	$	—
$3.55 – $5.41		1,212,567		5.24		672,930	$	5.34
$5.42 – $7.07		1,501,051		5.53		967,506	$	6.11
$7.20 – $9.41		1,199,546		7.17		551,162	$	9.06
$9.45 – $13.35		885,599		5.52		659,946	$	11.92
$13.54 – $15.00		1,148,250		6.26		668,752	$	14.07
$15.11 – $18.26		178,000		7.31		124,561	$	16.41
$19.51 – $19.51		10,000		6.14		9,583	$	19.51
$19.80 – $19.80		12,500		6.23		11,718	$	19.80
		8,287,456		6.69		3,881,078	$	8.99

Summary of Restricted Stock Unit Activity

A summary of Sangamo’s RSU activity is as follows:

	Number			Weighted Average
	of			Remaining		Aggregate Intrinsic
	Shares			Contractual Term		Value
				(In years)		(In thousands)
RSUs outstanding at December 31, 2016		321,816
RSUs awarded		12,600
RSUs released		(112,917	)
RSUs forfeited		(141,327	)
RSUs outstanding at December 31, 2017		80,172			0.90	$	1,315
RSUs vested and expected to vest at December 31, 2017		80,172			0.90	$	1,315

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Summary of Benefit for Income Taxes

The benefit for income taxes consisted of the following (in thousands):

	Year Ended December 31,
	2017		2016			2015
Benefit for income taxes:
Current:
Federal	$	—	$	—		$	—
State		—		—			—
Subtotal		—		—			—
Deferred:
Federal	$	—	$	(12	)	$	(5,563	)
State		—		(2	)		(159	)
Subtotal		—		(14	)		(5,722	)
Income tax benefit	$	—	$	(14	)	$	(5,722	)

Schedule of Difference Between Benefit for Income Taxes and Federal Statutory Income Tax Rate

The difference between the benefit for income taxes and the amount computed by applying the federal statutory income tax rate (34%) to loss before taxes is explained as follows (in thousands):

	Year Ended December 31,
	2017			2016			2015
Tax at federal statutory rate	$	(18,553	)	$	(24,369	)	$	(15,785	)
State taxes, net		795			(747	)		4,840
Federal Rate Change		53,045			—			—
Non-deductible stock compensation		2,120			2,781			1,085
Research credits		(869	)		(1,424	)		(814	)
Change in valuation allowance		(36,575	)		23,773			5,043
Other		37			(28	)		(91	)
Income tax benefit	$	—		$	(14	)	$	(5,722	)

Schedule of Company's Deferred Tax Assets

Significant components of the Company’s deferred tax assets are as follows (in thousands):

	December 31 ,
	2017		2016
Assets:
Deferred tax assets:
Net operating loss carryforwards	$	91,308	$	114,222
Research and development tax credit carryforwards		15,147		12,518
Stock-based compensation		3,168		8,565
Deferred revenue		934		2,918
Other		2,276		3,492
Total deferred tax asset		112,833		141,715
Valuation allowance		112,833		141,715
Net deferred tax assets	$	—	$	—
Liabilities:
Net deferred tax liability related to intangible assets		—		—
Total deferred tax liability	$	—	$	—

Summary of Activity Related to Company's Unrecognized Tax Benefits

The following table summarizes the activity related to the Company’s unrecognized tax benefits (in thousands):

	December 31,
	2017			2016			2015
Beginning balance	$	5,045		$	8,330		$	3,438
Additions based on tax positions related to the current year		622			1,023			557
Additions for tax positions of prior years		(8	)		27			4,335
Reductions for tax positions of prior years		—			(4,335	)		—
Ending balance	$	5,659		$	5,045		$	8,330

Accounts Payable and Accrued Liabilities (Tables)

12 Months Ended

Dec. 31, 2017

Payables And Accruals [Abstract]

Summary of Accounts Payable and Accrued Liabilities

Accounts payable and accrued liabilities consist of the following (in thousands):

	December 31 ,
	2017		2016
Accounts payable	$	16	$	2,580
Accrued research and development expenses		7,898		2,887
Accrued professional fees		1,318		270
Deferred rent		417		498
Other		1,386		26
Total accounts payable and accrued liabilities	$	11,035	$	6,261

Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Summary of Quarterly Financial Data

The following table sets forth certain unaudited quarterly financial data for the eight quarters ended December 31, 2016.

	2017												2016
	Q1			Q2			Q3			Q4			Q1			Q2			Q3			Q4
Revenues	$	3,425		$	8,253		$	11,812		$	13,077		$	3,942		$	3,702		$	2,823		$	8,922
Expenses	$	20,217		$	21,021		$	24,847		$	26,843		$	20,623		$	30,544		$	22,029		$	18,752
Net loss	$	(16,632	)	$	(12,491	)	$	(12,354	)	$	(13,091	)	$	(16,494	)	$	(26,575	)	$	(18,965	)	$	(9,624	)
Net loss per share	$	(0.23	)	$	(0.17	)	$	(0.15	)	$	(0.15	)	$	(0.23	)	$	(0.38	)	$	(0.27	)	$	(0.14	)

Organization and Summary of Significant Accounting Policies - Additional Information (Detail) $ / shares in Units, $ in Thousands		1 Months Ended		12 Months Ended
	May 10, 2017 USD ($)	Jan. 31, 2014 USD ($)	Jan. 31, 2012 USD ($)	Dec. 31, 2017 USD ($) Segments shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) shares
Organization and Summary of Significant Accounting Policies [Line Items]
Liquid investments purchased with original maturities				three months or less
Percentage of likelihood of indefinite lived intangible assets being impaired				50.00%
Impairment charge						$ 1,870
Change in fair value of contingent liability						$ (1,800)
Stock options and restricted stock units outstanding \| shares				8,367,628	9,578,322	9,008,185
Number of operating segments \| Segments				1
Bioverativ Inc [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Revenue recognized				$ 1,769	$ 2,321	$ 6,176
Up-front payment received from agreement		$ 20,000
Bioverativ Inc [Member] \| Customer Concentration Risk [Member] \| Total revenues [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Percentage of revenues				34.00%	46.00%
Bioverativ Inc [Member] \| Collaboration Contract Performance Period
Organization and Summary of Significant Accounting Policies [Line Items]
Increase in basic net loss per share \| $ / shares					$ 0.06
Decrease in revenues				$ 4,300	$ 4,300
Pfizer [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Revenue recognized				17,000
Up-front payment received from agreement	$ 70,000
Pfizer [Member] \| ASU No. 2014-09 [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Revenue recognized				$ 17,000
Up-front payment received from agreement	$ 70,000
Pfizer [Member] \| Customer Concentration Risk [Member] \| Total revenues [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Percentage of revenues				47.00%
Dow Agro Sciences [Member] \| Customer Concentration Risk [Member] \| Total revenues [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Percentage of revenues					26.00%
Shire AG [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Revenue recognized				$ 2,333	$ 2,181	$ 2,167
Up-front payment received from agreement			$ 13,000
Shire AG [Member] \| Customer Concentration Risk [Member] \| Total revenues [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Percentage of revenues					17.00%	40.00%
Biogen Inc [Member] \| Customer Concentration Risk [Member] \| Total revenues [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Percentage of revenues						35.00%
Minimum [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated useful lives of related assets				3 years
Maximum [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated useful lives of related assets				5 years
Maximum [Member] \| ASU No. 2014-09 [Member] \| Pro Forma [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated impact of the adoption of standard				$ 5,000

Fair Value Measurement - Summary of Fair Value Measurements of Cash Equivalents, Available-for-Sale Securities and Contingent Consideration Liability (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	$ 223,379	$ 139,466
Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	24,290	18,992
Commercial paper securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	4,595
Fair value on recurring basis [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	28,885	18,992
Total marketable securities	194,494	120,474
Total cash equivalents and marketable securities	223,379	139,466
Fair value on recurring basis [Member] \| Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	24,290	18,992
Fair value on recurring basis [Member] \| Commercial paper securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	4,595
Total marketable securities	110,247	23,185
Fair value on recurring basis [Member] \| Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	24,290	18,992
Total cash equivalents and marketable securities	24,290	18,992
Fair value on recurring basis [Member] \| Level 1 [Member] \| Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	24,290	18,992
Fair value on recurring basis [Member] \| Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	4,595
Total marketable securities	194,494	120,474
Total cash equivalents and marketable securities	199,089	120,474
Fair value on recurring basis [Member] \| Level 2 [Member] \| Commercial paper securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	4,595
Total marketable securities	110,247	23,185
Fair value on recurring basis [Member] \| Corporate debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	75,755	10,004
Fair value on recurring basis [Member] \| Corporate debt securities [Member] \| Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	75,755	10,004
Fair value on recurring basis [Member] \| U.S. government sponsored entity debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	8,492	87,285
Fair value on recurring basis [Member] \| U.S. government sponsored entity debt securities [Member] \| Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	$ 8,492	$ 87,285

Fair Value Measurement - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)
Fair Value Disclosures [Abstract]
Decrease in the total fair value of contingent consideration	$ (1,800)

Marketable Securities - Summary of Cash Equivalents and Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	$ 49,826	$ 22,061	$ 69,482	$ 6,030
Amortized Cost	223,634	139,416
Gross Unrealized Gains		76
Gross Unrealized (Losses)	(255)	(26)
Estimated Fair Value	223,379	139,466
Available-for-sale securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	194,749	120,424
Gross Unrealized Gains		76
Gross Unrealized (Losses)	(255)	(26)
Estimated Fair Value	194,494	120,474
Money market funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	24,290	18,992
Total cash equivalents	24,290	18,992
Commercial paper securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	4,595
Total cash equivalents	4,595
Commercial paper securities [Member] \| Available-for-sale securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	110,365	23,112
Gross Unrealized Gains		73
Gross Unrealized (Losses)	(118)
Estimated Fair Value	110,247	23,185
Cash equivalents [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	28,885	18,992
Total cash equivalents	28,885	18,992
Corporate debt securities [Member] \| Available-for-sale securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	75,886	10,005
Gross Unrealized (Losses)	(131)	(1)
Estimated Fair Value	75,755	10,004
U.S. government sponsored entity debt securities [Member] \| Available-for-sale securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	8,498	87,307
Gross Unrealized Gains		3
Gross Unrealized (Losses)	(6)	(25)
Estimated Fair Value	$ 8,492	$ 87,285

Marketable Securities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investments Debt And Equity Securities [Abstract]
Investments maturity period	2 years
Realized losses from the sale of available-for-sale securities	$ 0	$ 0	$ 0
Investments other-than-temporarily impaired	$ 0	$ 0

Stock-Based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 9,089	$ 15,057	$ 11,730
Research and development [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	5,031	6,463	6,444
General and administrative [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 4,058	$ 8,594	$ 5,286

Stock-Based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total compensation cost related to unvested stock options and RSU	$ 16,100,000
Weighted-average period of unvested stock options and RSU	2 years 9 months 14 days
Capitalized stock-based employee compensation expense	$ 0	$ 0	$ 0
Weighted-average estimated fair value per share of options granted	$ 4.10	$ 3.14	$ 5.72
Issuance of common stock under employee stock purchase plan, shares	253,994	202,711	128,181
Stock issued under employee stock purchase plans, average exercise price	$ 3.22	$ 4.04	$ 7.10
Weighted-average estimated fair value of shares purchased under ESPP plan	$ 2.37	$ 2.27	$ 4.42
Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total compensation cost related to unvested stock options and RSU	$ 700,000
Weighted-average period of unvested stock options and RSU	1 year 10 days

Stock-Based Compensation - Assumptions Used for Estimating Fair Value of Employee Stock Options (Detail) - Employee Stock Options [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend yield of stock	0.00%	0.00%	0.00%
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	1.81%	1.13%	1.46%
Expected life of option (in years)	5 years 8 months 23 days	5 years 3 months 10 days	5 years 3 months
Expected volatility	0.71%	0.68%	0.66%
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	2.28%	1.61%	1.58%
Expected life of option (in years)	5 years 9 months 29 days	5 years 3 months 14 days	5 years 3 months 21 days
Expected volatility	0.72%	0.70%	0.67%

Stock-Based Compensation - Weighted-Average Assumptions Used for Estimating Fair Value of ESPP Purchased Rights (Detail) - 2010 Employee Stock Purchase Plan [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend yield of stock	0.00%	0.00%	0.00%
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	0.44%	0.41%	0.06%
Expected life of option (in years)	6 months	6 months	6 months
Expected volatility	0.66%	0.71%	0.55%
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	0.76%	0.80%	0.33%
Expected life of option (in years)	2 years	2 years	2 years
Expected volatility	0.82%	0.76%	0.70%

Major Customers, Partnerships and Strategic Alliances - Additional Information (Detail)			1 Months Ended			12 Months Ended
	Dec. 28, 2017 USD ($)	May 10, 2017 USD ($)	Jan. 31, 2014 USD ($) Program	Jun. 30, 2012 Targets	Jan. 31, 2012 USD ($) Targets	Dec. 31, 2017 USD ($) Product	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of research programs \| Program			2
Pfizer [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement		$ 70,000,000
Potential amount eligible to receive for certain milestones		208,500,000
Milestone revenue receivable		475,000,000
Milestone payments received						$ 0
Number of products approved \| Product						0
Royalty revenues						$ 0
Research program to develop laboratory research reagents						32 months
Deferred revenue						$ 53,000,000
Recognition of upfront fee						17,000,000
Bioverativ Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement			$ 20,000,000
Potential amount eligible to receive for certain milestones			115,800,000
Potential amount to be funded for achievement of specified commercialized and sales milestones			$ 160,500,000
Milestone payments received						$ 0
Number of products approved \| Product						0
Royalty revenues						$ 0
Research program to develop laboratory research reagents						44 months
Deferred revenue						$ 4,600,000
Recognition of upfront fee						1,769,000	$ 2,321,000	$ 6,176,000
Shire AG [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement					$ 13,000,000
Deferred revenue						2,300,000
Recognition of upfront fee						$ 2,333,000	$ 2,181,000	2,167,000
Aggregate number of gene targets \| Targets					7
Number of initial gene targets \| Targets					4
Number of gene targets \| Targets				5
Number of additional gene targets \| Targets				2
Recognition of milestone									$ 1,000,000
Amount reimbursed and recognized related to prior obligations								$ 3,400,000
SB-525 [Member] \| Pfizer [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Potential amount to be funded for achievement of specified commercialized and sales milestones		266,500,000
C9ORF72 [Member] \| Pfizer [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement	$ 12,000,000
Maximum [Member] \| SB-525 [Member] \| Pfizer [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone revenue receivable		300,000,000
Maximum [Member] \| Other Products [Member] \| Pfizer [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone revenue receivable		$ 175,000,000
Maximum [Member] \| C9ORF72 [Member] \| Pfizer [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Potential amount eligible to receive for certain milestones	60,000,000
Potential amount to be funded for achievement of specified commercialized and sales milestones	$ 90,000,000

Major Customers, Partnerships and Strategic Alliances - Revenues Recognized under Agreement (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Bioverativ Inc [Member]
Revenues:
Recognition of upfront fee	$ 1,769,000	$ 2,321,000	$ 6,176,000
Royalty revenues	0
Research services	10,489,000	6,565,000	7,769,000
Total	12,258,000	8,886,000	13,945,000
Shire AG [Member]
Revenues:
Recognition of upfront fee	2,333,000	2,181,000	2,167,000
Research services	116,000	1,096,000	13,584,000
Total	2,449,000	3,277,000	15,751,000
Sigma-Aldrich Corporation [Member]
Revenues:
Royalty revenues	452,000	137,000	390,000
License fee revenues	267,000	1,140,000	4,463,000
Total	$ 719,000	$ 1,277,000	$ 4,853,000

Major Customers, Partnerships and Strategic Alliances - Agreement with Sigma-Aldrich Corporation - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2009	Dec. 31, 2017	Dec. 31, 2007
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Common stock issued under license agreement		$ 81,573
Sigma-Aldrich Corporation [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Developed laboratory research reagents, research services period			3 years
Upfront license fee	$ 20,000
Public offering, common stock shares issued	636,133
Reduced royalty rate	10.50%
Funding available under the amended agreement	$ 25,000
Sigma-Aldrich Corporation [Member] \| Upfront license fee [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront license fee	15,100
Common stock issued under license agreement	$ 4,900
Sigma-Aldrich Corporation [Member] \| License agreement terms [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement		$ 5,000

Major Customers, Partnerships and Strategic Alliances - Agreement with Dow AgroSciences in Plant Agriculture - Additional Information (Detail) - Dow Agro Sciences [Member] - License agreement terms [Member] - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2005
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research program to develop laboratory research reagents				3 years
One-time license fee earned on exercise of option				$ 6,000,000
Royalty revenues				$ 2,300,000
Percentage of royalties to be received from sublicensing				25.00%
Previously agreed research, development and commercialization milestone payments, and royalties on sales of products				$ 4,000,000
Fee due				$ 25,300,000
Minimum license annual fees specific reckoning period				11 years
Revenue attributable to research and development	$ 3,000,000	$ 5,100,000	$ 3,000,000
Minimum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Annual fees				$ 250,000
Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Annual fees				$ 3,000,000

Acquisition of Ceregene - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Oct. 31, 2013	Dec. 31, 2017	Dec. 31, 2015	Dec. 31, 2016	Mar. 31, 2015
Business Acquisition [Line Items]
Impairment charge			$ 1,870,000
Goodwill		$ 1,585,000		$ 1,585,000
Ceregene, Inc. [Member]
Business Acquisition [Line Items]
Common stock, transferred, shares	100,000
Sangamo shares of common stock	$ 1,200,000
Contingent earn-out	1,500,000
Fair value of contingent earn-out liability	1,800,000				$ 0
Estimated fair values of in-process research and development	1,900,000
Impairment charge			$ 1,900,000
Goodwill	$ 1,600,000
Goodwill impairment recognized		$ 0

Property and Equipment - Summary of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	$ 16,367	$ 12,048
Less accumulated depreciation and amortization	(6,951)	(5,639)
Property and equipment, net	31,066	6,557
Laboratory equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	7,572	6,206
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	1,494	636
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	3,425	1,330
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	3,876	3,876
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, net	$ 21,650	$ 148

Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Nov. 30, 2017
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 1,498	$ 997	$ 988
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Costs capitalized	300
Richmond Build-to-Suit Lease [Member]
Property, Plant and Equipment [Line Items]
Costs capitalized		$ 3,900
Brisbane Build-to-Suit Lease [Member]
Property, Plant and Equipment [Line Items]
Costs capitalized	21,200
Brisbane Build-to-Suit Lease [Member] \| Building [Member]
Property, Plant and Equipment [Line Items]
Costs capitalized	$ 20,900			$ 20,900

Commitments and Contingencies - Additional Information (Detail) $ in Millions	1 Months Ended	12 Months Ended
	Nov. 30, 2017 ft²	Dec. 31, 2017 USD ($) ft² Property	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Commitments And Contingencies [Line Items]
Additional property available under lease \| Property		3
Number of built-to-suit lease properties \| Property		2
Rent expenses \| $		$ 1.1	$ 1.0	$ 0.9
Intellectual Property [Member]
Commitments And Contingencies [Line Items]
License commitments \| $		$ 5.2
Richmond Build-to-Suit Lease [Member]
Commitments And Contingencies [Line Items]
Lease expiration date		Dec. 31, 2021
Property leased \| ft²		41,400
Brisbane Build-to-Suit Lease [Member]
Commitments And Contingencies [Line Items]
Lease expiration date		May 31, 2029
Property leased \| ft²	87,700	87,700
Brisbane Build-to-Suit Lease [Member] \| Tenant Improvements [Member]
Commitments And Contingencies [Line Items]
Other commitments for next twelve months \| $		$ 8.8
Services Agreement to Provide Dedicated Capacity to Supply Preclinical and Clinical Programs [Member] \| Tenant Improvements [Member]
Commitments And Contingencies [Line Items]
Other commitments for next twelve months \| $		$ 8.7
Operating Lease One [Member] \| Research and Office Space [Member]
Commitments And Contingencies [Line Items]
Area of space leased \| ft²		7,700
Lease expiration date		Aug. 31, 2019
Operating Lease Two [Member]
Commitments And Contingencies [Line Items]
Area of space leased \| ft²		6,200
Lease expiration date		Jul. 31, 2021

Commitments and Contingencies - Summary of Future Minimum Payments under Contractual Obligations (Detail) $ in Thousands	Dec. 31, 2017 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2018	$ 1,685
2019	2,925
2020	3,795
2021	3,798
2022	3,335
Thereafter	23,896
Total minimum payments	$ 39,434

Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Thousands			3 Months Ended	12 Months Ended
	Jun. 26, 2017 USD ($) $ / shares shares	Jun. 22, 2015 shares	Mar. 31, 2017 USD ($) shares	Dec. 31, 2017 USD ($) Installment $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Nov. 10, 2017 shares	May 26, 2017 USD ($)	Dec. 07, 2016 USD ($)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Preferred shares authorized				5,000,000
Net proceeds from issuance of common stock, after deducting offering expenses \| $				$ 81,573
Stock option maximum term				4 years 1 month 17 days
Specified stockholder ownership percentage				10.00%
Purchase price of common stock percent under stock incentive plans for specified stockholder				110.00%
Stock option maximum term for specified stockholder				5 years
Share of common stock subject to a stock option or stock appreciation right				100.00%
Fixed ratio shares of common stock				1.33
Intrinsic value of options exercised \| $				$ 12,300	$ 100	$ 6,400
Options outstanding, Aggregate Intrinsic Value \| $				71,658
Options exercisable, Aggregate Intrinsic Value \| $				28,864
Options vested and expected to vest, aggregate intrinsic value \| $				$ 71,700	0	14,000
Restricted stock units awarded				12,600
Total payments for the employees' tax obligations to taxing authorities \| $				$ 654	$ 776	$ 1,546
Share-Based Compensation Awards, Tranche 2 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options granted vesting percentage				0.33%
Share-Based Compensation Awards, Tranche 3 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options granted vesting percentage				0.33%
2013 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percent of fair value per share of common stock on option grant date				100.00%
Stock options vesting period				4 years
Stock options expiration term				10 years
Stock reserved for issuance under plan				14,100,000
Additional shares authorized under 2013 stock incentive plan		5,300,000		4,400,000
Shares reserved for issuance of future awards				3,601,633
2004 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock reserved for issuance under plan				9,700,000
Amended and Restated 2013 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock reserved for issuance under plan							1,000,000
2010 Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percent of fair value per share of common stock on option grant date				85.00%
Stock reserved for issuance under plan				2,100,000
Purchase plan offering period				2 years
Purchase plan purchase period				6 months
Shares reserved for issuance of future awards				835,674
Maximum [Member] \| 2013 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option maximum term				10 years
Employee Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares subject to repurchase rights				0
Employee Stock Options [Member] \| 2013 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based vesting rights				Options granted under the 2013 Plan generally vest over four years at a rate of 25 percent one year from the grant date and one thirty-sixth per month thereafter and expire ten years after the grant, or earlier upon employment termination.
Stock options granted vesting percentage				25.00%
Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based vesting rights				These awards generally vest as follows: one-third of the award will vest in a series of three successive equal annual installments.
Restricted stock units awarded				12,600	60,000	446,000
Grant date fair value per award of restricted stock units \| $ / shares				$ 15.85	$ 5.16	$ 9.45
Share-based compensation arrangement by share-based payment award, number of vesting installment \| Installment				3
Aggregate fair value of RSUs vested in period \| $				$ 1,200	$ 4,800	$ 4,100
Shares withheld from issuance in order to pay employee taxes				42,243	165,181	172,807
Restricted Stock Units (RSUs) [Member] \| Share-Based Compensation Awards, Tranche 1 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options granted vesting percentage				0.33%
ATM Agreement [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock issuable and sellable under offering agreement \| $								$ 75,000	$ 75,000
Common Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total shares issued	11,500,000			12,371,149
Public offering price of common stock issued \| $ / shares	$ 7.25
Net proceeds from issuance of common stock, after deducting offering expenses \| $	$ 78,100
Common Stock [Member] \| ATM Agreement [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total shares issued			871,149
Net proceeds from issuance of common stock, after deducting offering expenses \| $			$ 3,400
Commission paid to sales agent \| $			$ 100

Stockholders' Equity - Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options outstanding at December 31, 2016, Number of Shares \| shares	9,256,506
Options granted, Number of Shares \| shares	3,091,125
Options exercised, Number of Shares \| shares	(2,030,815)
Options canceled, Number of Shares \| shares	(2,029,360)
Options outstanding at December 31, 2017, Number of Shares \| shares	8,287,456
Options vested and expected to vest at December 31, 2017, Number of Shares \| shares	8,287,456
Options exercisable at December 31, 2017, Number of Shares \| shares	3,881,078
Options outstanding, Weighted-Average Exercise per Share Price, Beginning Balance \| $ / shares	$ 8.31
Options granted, Weighted-Average Exercise per Share Price \| $ / shares	6.48
Options exercised, Weighted-Average Exercise per Share Price \| $ / shares	7.76
Options canceled, Weighted-Average Exercise per Share Price \| $ / shares	8.28
Options outstanding, Weighted-Average Exercise per Share Price, Ending Balance \| $ / shares	7.77
Options vested and expected to vest at December 31, 2017, Weighted-Average Exercise Per Share Price \| $ / shares	7.77
Options exercisable at December 31, 2017, Weighted-Average Exercise per Share Price \| $ / shares	$ 8.99
Options outstanding at December, 31, 2017, Weighted Average Remaining Contractual Term	6 years 8 months 8 days
Options vested and expected to vest at December, 31, 2017, Weighted Average Remaining Contractual Term	6 years 8 months 8 days
Options exercisable at December, 31, 2017, Weighted Average Remaining Contractual Term	4 years 1 month 17 days
Options outstanding at December 31, 2017, Aggregate Intrinsic Value \| $	$ 71,658
Options vested and expected to vest at December 31, 2017, Aggregate Intrinsic Value \| $	71,658
Options exercisable at December 31, 2017, Aggregate Intrinsic Value \| $	$ 28,864

Stockholders' Equity - Summary of Stock Options Outstanding (Detail)	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Options Outstanding and Exercisable Number of Shares of common stock subject to options \| shares	8,287,456
Options Outstanding and Exercisable Weighted Average Remaining Contractual Life (In years)	6 years 8 months 8 days
Options Exercisable Number of Shares of common stock subject to options \| shares	3,881,078
Options Exercisable Weighted Average Exercise Price	$ 8.99
$2.55 – $3.45 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Lower Range of Exercise Price	2.55
Upper Range of Exercise Price	$ 3.45
Options Outstanding and Exercisable Number of Shares of common stock subject to options \| shares	612,318
Options Outstanding and Exercisable Weighted Average Remaining Contractual Life (In years)	7 years 11 months 1 day
Options Exercisable Number of Shares of common stock subject to options \| shares	214,920
Options Exercisable Weighted Average Exercise Price	$ 3.13
$3.50 – $3.50 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Lower Range of Exercise Price	3.50
Upper Range of Exercise Price	$ 3.50
Options Outstanding and Exercisable Number of Shares of common stock subject to options \| shares	1,527,625
Options Outstanding and Exercisable Weighted Average Remaining Contractual Life (In years)	9 years 25 days
$3.55 – $5.41 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Lower Range of Exercise Price	$ 3.55
Upper Range of Exercise Price	$ 5.41
Options Outstanding and Exercisable Number of Shares of common stock subject to options \| shares	1,212,567
Options Outstanding and Exercisable Weighted Average Remaining Contractual Life (In years)	5 years 2 months 26 days
Options Exercisable Number of Shares of common stock subject to options \| shares	672,930
Options Exercisable Weighted Average Exercise Price	$ 5.34
$5.42 – $7.07 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Lower Range of Exercise Price	5.42
Upper Range of Exercise Price	$ 7.07
Options Outstanding and Exercisable Number of Shares of common stock subject to options \| shares	1,501,051
Options Outstanding and Exercisable Weighted Average Remaining Contractual Life (In years)	5 years 6 months 10 days
Options Exercisable Number of Shares of common stock subject to options \| shares	967,506
Options Exercisable Weighted Average Exercise Price	$ 6.11
$7.20 – $9.41 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Lower Range of Exercise Price	7.20
Upper Range of Exercise Price	$ 9.41
Options Outstanding and Exercisable Number of Shares of common stock subject to options \| shares	1,199,546
Options Outstanding and Exercisable Weighted Average Remaining Contractual Life (In years)	7 years 2 months 1 day
Options Exercisable Number of Shares of common stock subject to options \| shares	551,162
Options Exercisable Weighted Average Exercise Price	$ 9.06
$9.45 – $13.35 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Lower Range of Exercise Price	9.45
Upper Range of Exercise Price	$ 13.35
Options Outstanding and Exercisable Number of Shares of common stock subject to options \| shares	885,599
Options Outstanding and Exercisable Weighted Average Remaining Contractual Life (In years)	5 years 6 months 7 days
Options Exercisable Number of Shares of common stock subject to options \| shares	659,946
Options Exercisable Weighted Average Exercise Price	$ 11.92
$13.54 – $15.00 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Lower Range of Exercise Price	13.54
Upper Range of Exercise Price	$ 15
Options Outstanding and Exercisable Number of Shares of common stock subject to options \| shares	1,148,250
Options Outstanding and Exercisable Weighted Average Remaining Contractual Life (In years)	6 years 3 months 3 days
Options Exercisable Number of Shares of common stock subject to options \| shares	668,752
Options Exercisable Weighted Average Exercise Price	$ 14.07
$15.11 – $18.26 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Lower Range of Exercise Price	15.11
Upper Range of Exercise Price	$ 18.26
Options Outstanding and Exercisable Number of Shares of common stock subject to options \| shares	178,000
Options Outstanding and Exercisable Weighted Average Remaining Contractual Life (In years)	7 years 3 months 21 days
Options Exercisable Number of Shares of common stock subject to options \| shares	124,561
Options Exercisable Weighted Average Exercise Price	$ 16.41
$19.51 – $19.51 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Lower Range of Exercise Price	19.51
Upper Range of Exercise Price	$ 19.51
Options Outstanding and Exercisable Number of Shares of common stock subject to options \| shares	10,000
Options Outstanding and Exercisable Weighted Average Remaining Contractual Life (In years)	6 years 1 month 20 days
Options Exercisable Number of Shares of common stock subject to options \| shares	9,583
Options Exercisable Weighted Average Exercise Price	$ 19.51
$19.80 – $19.80 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Lower Range of Exercise Price	19.80
Upper Range of Exercise Price	$ 19.80
Options Outstanding and Exercisable Number of Shares of common stock subject to options \| shares	12,500
Options Outstanding and Exercisable Weighted Average Remaining Contractual Life (In years)	6 years 2 months 23 days
Options Exercisable Number of Shares of common stock subject to options \| shares	11,718
Options Exercisable Weighted Average Exercise Price	$ 19.80

Stockholders' Equity - Summary of Restricted Stock Unit Activity (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
RSUs outstanding at December 31, 2016, Number of Shares	321,816
RSUs awarded, Number of Shares	12,600
RSUs released, Number of Shares	(112,917)
RSUs forfeited, Number of Shares	(141,327)
RSUs outstanding at December 31, 2017, Number of Shares	80,172
RSUs vested and expected to vest at December 31, 2017, Number of Shares	80,172
RSUs outstanding at December, 31, 2017, Weighted Average Remaining Contractual Term	10 months 24 days
RSUs vested and expected to vest at December 31, 2017, Weighted Average Remaining Contractual Term	10 months 24 days
RSUs outstanding at December 31, 2017, Aggregate Intrinsic Value \| $	$ 1,315
RSUs vested and expected to vest at December 31, 2017, Aggregate Intrinsic Value \| $	$ 1,315

Income Taxes - Summary of Benefit for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Deferred:
Federal	$ (12)	$ (5,563)
State	(2)	(159)
Subtotal	(14)	(5,722)
Income tax benefit	$ (14)	$ (5,722)

Income Taxes - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Federal statutory income tax rate			34.00%
Claim settlement received	$ 14,500,000				$ 14,452,000
Settlement recognized as additional paid-in capital, net of tax					9,495,000
Income tax benefit, claims settlement					5,000,000
Increase (decrease) in deferred tax assets valuation allowance			$ (28,900,000)	$ 23,800,000	$ 5,000,000
Deferred tax assets, net operating loss carryforwards for federal			475,000,000
Deferred tax assets, net operating loss carryforwards for state			142,000,000
Federal research tax credit carryforwards			10,800,000
State research tax credit carryforwards			$ 11,800,000
Tax credit carryforward, expiration year			2018
Federal tax rate reduction net of valuation allowance			$ 0
Accrued interest and/or penalties			$ 0
Maximum [Member]
Income Taxes [Line Items]
Federal statutory income tax rate			35.00%
Scenario Plan [Member]
Income Taxes [Line Items]
Federal statutory income tax rate		21.00%
State [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year			2018
Federal [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year			2017

Income Taxes - Schedule of Difference Between Benefit for Income Taxes and Federal Statutory Income Tax Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Tax at federal statutory rate	$ (18,553)	$ (24,369)	$ (15,785)
State taxes, net	795	(747)	4,840
Federal Rate Change	53,045
Non-deductible stock compensation	2,120	2,781	1,085
Research credits	(869)	(1,424)	(814)
Change in valuation allowance	(36,575)	23,773	5,043
Other	$ 37	(28)	(91)
Income tax benefit		$ (14)	$ (5,722)

Income Taxes - Schedule of Company's Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Net operating loss carryforwards	$ 91,308	$ 114,222
Research and development tax credit carryforwards	15,147	12,518
Stock-based compensation	3,168	8,565
Deferred revenue	934	2,918
Other	2,276	3,492
Total deferred tax asset	112,833	141,715
Valuation allowance	$ 112,833	$ 141,715

Income Taxes - Summary of Activity Related to Company's Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Beginning balance	$ 5,045	$ 8,330	$ 3,438
Additions based on tax positions related to the current year	622	1,023	557
Additions for tax positions of prior years	(8)	27	4,335
Reductions for tax positions of prior years		(4,335)
Ending balance	$ 5,659	$ 5,045	$ 8,330

Accounts Payable and Accrued Liabilities - Summary of Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables And Accruals [Abstract]
Accounts payable	$ 16	$ 2,580
Accrued research and development expenses	7,898	2,887
Accrued professional fees	1,318	270
Deferred rent	417	498
Other	1,386	26
Total accounts payable and accrued liabilities	$ 11,035	$ 6,261

Employee Benefit Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compensation And Retirement Disclosure [Abstract]
Defined contribution plan, employer's matching contribution percent	50.00%
Percentage of employer matching contribution to employee contribution	8.00%	6.00%	6.00%
Maximum percentage limit of employee contributions	8.00%	6.00%	6.00%
Defined contribution plan, maximum employer's contribution per employee	$ 4,000	$ 3,000	$ 3,000
Aggregate employers contributions to defined contribution plan	$ 500,000	$ 300,000	$ 300,000

Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Selected Quarterly Financial Information [Abstract]
Revenues	$ 13,077	$ 11,812	$ 8,253	$ 3,425	$ 8,922	$ 2,823	$ 3,702	$ 3,942	$ 36,567	$ 19,389	$ 39,539
Expenses	26,843	24,847	21,021	20,217	18,752	22,029	30,544	20,623	92,928	91,948	86,395
Net loss	$ (13,091)	$ (12,354)	$ (12,491)	$ (16,632)	$ (9,624)	$ (18,965)	$ (26,575)	$ (16,494)	$ (54,568)	$ (71,658)	$ (40,703)
Net loss per share	$ (0.15)	$ (0.15)	$ (0.17)	$ (0.23)	$ (0.14)	$ (0.27)	$ (0.38)	$ (0.23)	$ (0.70)	$ (1.02)	$ (0.58)

Build-to-Suit Lease - Additional Information (Detail) $ in Millions	1 Months Ended		12 Months Ended
	Nov. 30, 2017 USD ($) ft² Option	Dec. 31, 2015 ft² Option	Dec. 31, 2017 USD ($) ft²	Dec. 31, 2016 USD ($)
Brisbane Build-to-Suit Lease [Member]
Operating Leased Assets [Line Items]
Property leased \| ft²	87,700		87,700
Lease expiration date			May 31, 2029
Operating lease expiration period	10 years
Number of lease term extension options \| Option	2
Letter of credit	$ 3.5
Costs capitalized			$ 21.2
Brisbane Build-to-Suit Lease [Member] \| Building [Member]
Operating Leased Assets [Line Items]
Costs capitalized	$ 20.9		$ 20.9
Brisbane Build-to-Suit Lease [Member] \| Maximum [Member]
Operating Leased Assets [Line Items]
Lease agreement, extendable lease term	10 years
Point Pinole Build-to-Suit Lease [Member]
Operating Leased Assets [Line Items]
Property leased \| ft²		41,400
Lease expiration date			Dec. 31, 2021
Operating lease expiration period		5 years
Number of lease term extension options \| Option		2
Costs capitalized				$ 3.9
Point Pinole Build-to-Suit Lease [Member] \| Maximum [Member]
Operating Leased Assets [Line Items]
Lease agreement, extendable lease term		10 years

Claims Settlement - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2016	Dec. 31, 2015
Claims Settlement [Line Items]
Claim settlement received	$ 14,500		$ 14,452
Settlement recognized as additional paid-in capital, net of tax			9,495
Benefit from income taxes		$ 14	5,722
Disgorgement settlement [Member]
Claims Settlement [Line Items]
Benefit from income taxes			$ 5,000

Subsequent Event - Additional Information (Detail) - Kite Pharma, Inc. ("Kite") [Member] - Collaboration and License Agreement [Member] - Subsequent Event [Member]	1 Months Ended
	Feb. 28, 2018 USD ($)
Subsequent Event [Line Items]
Milestone revenue receivable	$ 150,000,000
Maximum [Member]
Subsequent Event [Line Items]
Contingent development - and sales-based milestone payments to be received	3,010,000,000
Achievement of Specified Research, Clinical Development, Regulatory and First Commercial Sale Milestones [Member]
Subsequent Event [Line Items]
Contingent development - and sales-based milestone payments to be received	1,260,000,000
Achievement of Specified Sales-based Milestones if Annual Worldwide Net Sales of Licensed Products Reach Specified Levels [Member]
Subsequent Event [Line Items]
Contingent development - and sales-based milestone payments to be received	$ 1,750,000,000