Short-term Investments - Short-term Investments Available-for-sale Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013
Schedule Of Short Term Investments And Available For Sale Securities [Line Items]
Amortized cost	$ 32,693
Gross unrealized gains	25
Gross unrealized losses	(3)
Fair value	32,715
U.S. Government-related Debt Securities [Member]
Schedule Of Short Term Investments And Available For Sale Securities [Line Items]
Amortized cost	1,565
Gross unrealized gains	1
Gross unrealized losses
Fair value	1,566
Corporate Debt Securities [Member]
Schedule Of Short Term Investments And Available For Sale Securities [Line Items]
Amortized cost	31,128
Gross unrealized gains	24
Gross unrealized losses	(3)
Fair value	$ 31,149