Short-term Investments - Summary of Amortized Cost, Gross Unrealized Gains and Losses and Fair Value of Short-term Investments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 95,469
Gross Unrealized Gains
Gross Unrealized Losses	(15)
Aggregate Fair Value	95,454
U.S. Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	87,453
Gross Unrealized Gains
Gross Unrealized Losses	(11)
Aggregate Fair Value	87,442
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,999
Gross Unrealized Gains
Gross Unrealized Losses
Aggregate Fair Value	5,999
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,017
Gross Unrealized Gains
Gross Unrealized Losses	(4)
Aggregate Fair Value	$ 2,013