Common Stock Warrants - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Equity [Abstract]
Issuance of common stock upon exercise of warrants	0	9,703	0	132,295
Issuance of common stock upon exercise of warrants on cash basis		74,136
Proceeds from issuance of common stock upon warrant exercises		$ 400		$ 426
Issuance of common stock in accordance with net exercise provisions		58,159
Fair value reclassification of warrant liability to additional paid-in capital		$ 200		$ 1,500