Warrants Outstanding (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Class of Warrant or Right [Line Items]
Number of shares	$ 8,574
March 2008 Financing
Class of Warrant or Right [Line Items]
Number of shares	4,372
Exercise Price	2.77
Expiration Date	Mar. 25, 2015
March 2012 Warrant Exchange
Class of Warrant or Right [Line Items]
Number of shares	$ 4,202
Exercise Price	4.05
Expiration Date	Mar. 29, 2015