Notes Payable - Carrying Value of MHR Obligations (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Unamortized discounts	$ (11,041)	$ (7,196)
Notes payable, total	61,172	44,546
Amended and Restated Convertible Notes [Member]
Debt Instrument [Line Items]
Notes payable, total	46,542	40,897
Loan Agreement [Member]
Debt Instrument [Line Items]
Notes payable, total	22,801	8,307
Amended and Restated Reimbursement Notes [Member]
Debt Instrument [Line Items]
Notes payable, total	755	683
Amended and Restated Bridge Notes [Member]
Debt Instrument [Line Items]
Notes payable, total	$ 2,115	$ 1,855