Fair Value of Financial Instruments - Schedule of Fair Value of the Liabilities Categorized as Level 3 Instruments (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Convertible Preferred Stock Warrants [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at the beginning of the period		$ 1,516
Unrealized gain included in other income (expense)		(587)
Reclassification to common stock warrants		(929)
Balance at the end of the period
Derivative Liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at the beginning of the period	196
Portion of convertible note allocated to derivative	35	196
Remeasurement of derivative liability upon conversion of underlying note	(231)
Balance at the end of the period		$ 196