Stock Warrants - Schedule of Common and Convertible Preferred Stock Warrant Activity of the Company (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Common Stock Warrant [Member]
Class of Warrant or Right [Line Items]
Beginning Balance	2,842	2,640	2,937
Conversion (in shares)		302
Conversion (per share)		$ 3.50
Expired (in shares)			(1)
Exercised (in shares)	(65)	(100)	(296)
Ending Balance	2,777	2,842	2,640
Beginning Balance	3.05	2.98	2.93
Expired (per share)			$ 2.47
Exercised (per share)	$ 2.82	$ 2.63	$ 2.46
Ending Balance	3.05	3.05	2.98
Convertible Preferred Stock Warrants [Member]
Class of Warrant or Right [Line Items]
Beginning Balance		302	306
Conversion (in shares)		(302)
Conversion (per share)		$ 3.50
Exercised (in shares)			(4)
Ending Balance			302
Beginning Balance		3.50	3.48
Exercised (per share)			$ 1.89
Ending Balance			3.50