Available-for-Sale Marketable Securities - Summary of Available-for-Sale Marketable Securities by Major Type of Security (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 91,675
Gross Unrealized Gains	5
Gross Unrealized Losses	(40)
Estimated Fair Value	91,640
Money Market Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	42,017
Gross Unrealized Losses	(31)
Estimated Fair Value	41,986
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,528
Estimated Fair Value	2,528
Other U.S. Government Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,492
Gross Unrealized Gains	4
Estimated Fair Value	13,496
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,194
Gross Unrealized Losses	(6)
Estimated Fair Value	14,188
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,444
Gross Unrealized Gains	1
Gross Unrealized Losses	(3)
Estimated Fair Value	$ 19,442