Common Stock - Schedule of Shares Reserved for Future Issuance (Detail) - shares shares in Thousands	Dec. 31, 2015	Dec. 31, 2014
Common Stock Warrants [Member]
Class of Stock [Line Items]
Shares reserved for future issuance		2,381
Outstanding Options To Purchase Common Stock [Member]
Class of Stock [Line Items]
Shares reserved for future issuance	19,211	19,567
Stock Incentive Plan 2011 [Member]
Class of Stock [Line Items]
Shares reserved for future issuance	2,462	1,983
Conversion of the Convertible Notes [Member]
Class of Stock [Line Items]
Shares reserved for future issuance	25,000	25,000