Cash, Cash Equivalents, and Short-Term Investments - Summary of Cash, Cash Equivalents and Short-Term Investments (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	$ 136,320	$ 107,345
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	2	2
Cash and cash equivalents, Fair Value	136,318	107,343
Short-term investments, Amortized Cost	176,853	154,151
Short-term investments, Gross Unrealized Gains	1	3
Short-term investments, Gross Unrealized Losses	360	405
Short-term investments, Estimated Fair Value	176,494	153,749	[1]
Cash [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	65,293	63,642
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	65,293	63,642
Commercial Paper [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	4,996	6,995
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	2	2
Cash and cash equivalents, Fair Value	4,994	6,993
Short-term investments, Amortized Cost	20,175	14,245
Short-term investments, Gross Unrealized Gains	0	0
Short-term investments, Gross Unrealized Losses	8	8
Short-term investments, Estimated Fair Value	20,167	14,237
Money Market Funds [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	66,031	36,708
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	66,031	36,708
Corporate Debt Obligations [Member]
Schedule of Investments [Line Items]
Short-term investments, Amortized Cost	137,200	110,062
Short-term investments, Gross Unrealized Gains	1	0
Short-term investments, Gross Unrealized Losses	310	347
Short-term investments, Estimated Fair Value	136,891	109,715
US Government Agencies [Member]
Schedule of Investments [Line Items]
Short-term investments, Amortized Cost	18,998	18,998
Short-term investments, Gross Unrealized Gains	0	2
Short-term investments, Gross Unrealized Losses	42	50
Short-term investments, Estimated Fair Value	18,956	18,950
Bank Deposits [Member]
Schedule of Investments [Line Items]
Short-term investments, Amortized Cost	480	10,846
Short-term investments, Gross Unrealized Gains	0	1
Short-term investments, Gross Unrealized Losses	0	0
Short-term investments, Estimated Fair Value	$ 480	$ 10,847

[1] The Condensed Consolidated Balance Sheet as of December 31, 2016 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.