Fair Value Measurements - Company's Financial Assets and Liability Measured at Fair Value on a Recurring Basis (Detail) (Fair Value Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Liabilities
Warrant liability	$ 653	$ 374
Quoted Prices in Active Markets (Level 1) [Member]
Liabilities
Warrant liability
Significant Other Observable Inputs (Level 2) [Member]
Liabilities
Warrant liability
Significant Unobservable Inputs (Level 3) [Member]
Liabilities
Warrant liability	$ 653	$ 374