Preferred Stock and Stockholders' Equity - Common Stock Warrants Narrative (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended				12 Months Ended
	Dec. 31, 2014	Jul. 31, 2012	Jul. 31, 2011	Jun. 30, 2011	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2012	Jul. 27, 2012
Schedule Of Common Stock [Line Items]
Shares of common stock exercisable through warrants		1,973,025
Warrants exercise price (in usd per share)								$ 20.00
Term of common stock warrant exercisable		5 years	10 years
Fair value of warrant liabilities					$ 6,069	$ 724
Warrant exercisable to Healthcare Royalty, shares			28,125
Investment Warrants, Exercise Price			$ 72.00
Imputed interest on working capital advance						1,176
Healthcare Royalty Financing Agreement [Member]
Schedule Of Common Stock [Line Items]
Fair value of warrant liabilities					$ 127	$ 85
Oxford/SVB [Member]
Schedule Of Common Stock [Line Items]
Shares of common stock exercisable through warrants	63,559			3,306
Warrants exercise price (in usd per share)				$ 30.24	$ 9.44	$ 9.44
Term of common stock warrant exercisable	10 years			7 years
Warrants exercised	31,779
Imputed interest on working capital advance					$ 558		$ 76
Warrant [Member]
Schedule Of Common Stock [Line Items]
Warrants exercised					58,156
Common Stock [Member] | Oxford/SVB [Member]
Schedule Of Common Stock [Line Items]
Shares issued in period	16,719
Shares paid for tax withholding for share based compensation	15,060