Investments - Summary of Available-for-Sale Investments at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 9,791	$ 9,321
Gross Unrealized (Losses)	(3)	(7)
Gross Unrealized Gains	1
Estimated Fair Value	9,789	9,314
Short-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost		3,125
Estimated Fair Value		3,125
Short-term investments [Member] | Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	999	1,997
Estimated Fair Value	999	1,997
Short-term investments [Member] | Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	8,792	1,128
Gross Unrealized (Losses)	(3)
Gross Unrealized Gains	1
Estimated Fair Value	8,790	1,128
Long-term investments [Member] | Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost		6,196
Gross Unrealized (Losses)		(7)
Estimated Fair Value		$ 6,189