Fair Value Measurement - Summary of Fair Value Measurements of Cash Equivalents, and Available-for-Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	$ 124,407	$ 139,466
Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	10,632	18,992
Fair value on recurring basis [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	10,632	18,992
Total marketable securities	113,775	120,474
Total cash equivalents and marketable securities	124,407	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	10,632	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	24,394	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	10,632	18,992
Total cash equivalents and marketable securities	10,632	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	10,632	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	113,775	120,474
Total cash equivalents and marketable securities	113,775	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	24,394	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	6,001	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	6,001	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	83,380	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	$ 83,380	$ 87,285