Derivative Instruments - Components of Derivative Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Derivative [Line Items]
Derivative instruments	$ 15,509	$ 2,089
Amended and Restated Convertible Notes [Member]
Derivative [Line Items]
Derivative instruments	10,371	230
Amended and Restated Reimbursement Notes [Member]
Derivative [Line Items]
Derivative instruments	7
Amended and Restated Bridge Notes [Member]
Derivative [Line Items]
Derivative instruments	960
August 2009 Warrants [Member]
Derivative [Line Items]
Derivative instruments	597	372
June 2010 MHR Warrants [Member]
Derivative [Line Items]
Derivative instruments	249	79
Amended and Restated August 2010 Warrants [Member]
Derivative [Line Items]
Derivative instruments	420	277
August 2010 Investor Warrants [Member]
Derivative [Line Items]
Derivative instruments	171	258
August 2010 MHR Waiver Warrants [Member]
Derivative [Line Items]
Derivative instruments	156	103
July 2011 MHR Warrants [Member]
Derivative [Line Items]
Derivative instruments	482	340
July 2011 Warrants [Member]
Derivative [Line Items]
Derivative instruments	369	340
Amended and Restated July 2011 Warrants [Member]
Derivative [Line Items]
Derivative instruments	127	90
2013 MHR Modification Warrants [Member]
Derivative [Line Items]
Derivative instruments	$ 1,600