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Fair Value Measurement - Summary of Fair Value Measurements of Cash Equivalents, and Available-for-Sale Marketable Securities (Detail) - USD ($)
$ in Thousands
Mar. 31, 2016
Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Total cash equivalents $ 28,057 $ 65,937
Total marketable securities 155,575 139,518
Total cash equivalents and marketable securities 183,632 205,455
Money market funds [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Total cash equivalents 19,387 25,070
Commercial paper securities [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Total cash equivalents   2,000
Total marketable securities 32,468 30,717
Level 1 [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Total cash equivalents 28,057 65,937
Total cash equivalents and marketable securities 28,057 65,937
Level 1 [Member] | Money market funds [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Total cash equivalents 19,387 25,070
Level 1 [Member] | Commercial paper securities [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Total cash equivalents   2,000
Level 2 [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Total marketable securities 155,575 139,518
Total cash equivalents and marketable securities 155,575 139,518
Level 2 [Member] | Commercial paper securities [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Total marketable securities 32,468 30,717
U.S. government sponsored entity debt securities [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Total cash equivalents 8,670 38,867
Total marketable securities 108,548 91,538
U.S. government sponsored entity debt securities [Member] | Level 1 [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Total cash equivalents 8,670 38,867
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 108,548 91,538
Corporate debt securities [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Total marketable securities 14,559 17,263
Corporate debt securities [Member] | Level 2 [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Total marketable securities $ 14,559 $ 17,263