Investments - Summary of Available-for-Sale Investments at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 9,845	$ 9,321
Gross Unrealized (Losses)	(1)	(7)
Gross Unrealized Gains	4
Estimated Fair Value	9,848	9,314
Commercial paper due in one year or less [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	998	1,997
Estimated Fair Value	998	1,997
Corporate bonds due in one year or less [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	7,842	1,128
Gross Unrealized Gains	4
Estimated Fair Value	7,846	1,128
Total short-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	8,840	3,125
Gross Unrealized Gains	4
Estimated Fair Value	8,844	3,125
Total long-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	1,005	6,196
Gross Unrealized (Losses)	(1)	(7)
Estimated Fair Value	1,004	6,189
Corporate bonds due in one year or more [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost		6,196
Gross Unrealized (Losses)		(7)
Estimated Fair Value		$ 6,189