Cash, Cash Equivalents, and Short-Term Investments - Summary of Cash, Cash Equivalents and Short-Term Investments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	$ 65,802	$ 76,705
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	1	1
Cash and cash equivalents, Fair Value	65,801	76,704
Short-term investments, Amortized Cost	35,403	38,373
Short-term investments, Gross Unrealized Gains	16	22
Short-term investments, Gross Unrealized Losses	24	14
Short-term investments, Estimated Fair Value	35,395	38,381	[1]
Cash [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	18,508	41,973
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	18,508	41,973
Commercial Paper [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	23,448	21,948
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	1	1
Cash and cash equivalents, Fair Value	23,447	21,947
Corporate Debt Obligations [Member]
Schedule of Investments [Line Items]
Short-term investments, Amortized Cost	25,133	28,220
Short-term investments, Gross Unrealized Gains	16	22
Short-term investments, Gross Unrealized Losses	24	14
Short-term investments, Estimated Fair Value	25,125	28,228
Bank Deposits [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	11,017	10,165
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	11,017	10,165
Short-term investments, Amortized Cost	10,270	10,153
Short-term investments, Gross Unrealized Gains	0	0
Short-term investments, Gross Unrealized Losses	0	0
Short-term investments, Estimated Fair Value	10,270	10,153
Money Market Funds [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	12,829	2,619
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	$ 12,829	$ 2,619

[1] The Condensed Consolidated Balance Sheet as of December 31, 2013 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.