Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurement - Summary of Fair Value Measurements of Cash Equivalents, and Available-for-Sale Marketable Securities (Detail)

v3.7.0.1
Fair Value Measurement - Summary of Fair Value Measurements of Cash Equivalents, and Available-for-Sale Marketable Securities (Detail) - USD ($)
$ in Thousands
Jun. 30, 2017
Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Total cash equivalents and marketable securities $ 257,802 $ 139,466
Money market funds [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Total cash equivalents 61,385 18,992
Fair value on recurring basis [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Total cash equivalents 61,385 18,992
Total marketable securities 196,417 120,474
Total cash equivalents and marketable securities 257,802 139,466
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 61,385 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 marketable securities 65,444 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 61,385 18,992
Total cash equivalents and marketable securities 61,385 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 61,385 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 marketable securities 196,417 120,474
Total cash equivalents and marketable securities 196,417 120,474
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 marketable securities 65,444 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 64,907 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 64,907 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 66,066 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 $ 66,066 $ 87,285