Cash, Cash Equivalents, and Short-Term Investments - Summary of Cash, Cash Equivalents and Short-Term Investments (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	$ 158,693	$ 168,255
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	2	3
Cash and cash equivalents, Fair Value	158,691	168,252
Short-term investments, Amortized Cost	100,093	96,853
Short-term investments, Gross Unrealized Gains	28	2
Short-term investments, Gross Unrealized Losses	67	300
Short-term investments, Estimated Fair Value	100,054	96,555	[1]
Cash [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	51,182	57,906
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	51,182	57,906
Bank Deposits [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	10,262	10,253
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	10,262	10,253
Short-term investments, Amortized Cost	10,366	10,263
Short-term investments, Gross Unrealized Gains	0	0
Short-term investments, Gross Unrealized Losses	0	0
Short-term investments, Estimated Fair Value	10,366	10,263
Commercial Paper [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	20,921	13,896
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	2	3
Cash and cash equivalents, Fair Value	20,919	13,893
Short-term investments, Amortized Cost	11,548
Short-term investments, Gross Unrealized Gains	0
Short-term investments, Gross Unrealized Losses	0
Short-term investments, Estimated Fair Value	11,548
Money Market Funds [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	76,328	86,200
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	76,328	86,200
Corporate Debt Obligations [Member]
Schedule of Investments [Line Items]
Short-term investments, Amortized Cost	63,665	86,590
Short-term investments, Gross Unrealized Gains	16	2
Short-term investments, Gross Unrealized Losses	64	300
Short-term investments, Estimated Fair Value	63,617	$ 86,292
US Government Agencies [Member]
Schedule of Investments [Line Items]
Short-term investments, Amortized Cost	14,514
Short-term investments, Gross Unrealized Gains	12
Short-term investments, Gross Unrealized Losses	3
Short-term investments, Estimated Fair Value	$ 14,523

[1] The Condensed Consolidated Balance Sheet as of December 31, 2015 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.