Stock Incentive Plans - Summary of Activity of Stock Incentive and Equity Plans (Detail) - $ / shares	1 Months Ended	4 Months Ended		5 Months Ended	12 Months Ended
	Sep. 30, 2016	Apr. 30, 2016	Jul. 31, 2015	Jul. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Shares available for grant
Shares available for grant, Beginning balance		732,270			732,270	1,772,529
Shares available for grant, Authorized					1,900,000
Shares available for grant, Granted					(1,537,692)	(1,457,826)
Shares available for grant, Exercised/issued					0	0
Shares available for grant, Canceled/forfeited					1,337,606	417,567
Shares available for grant, Ending balance					2,432,184	732,270
Number of options outstanding
Number of options outstanding, Beginning balance		2,851,568			2,851,568	2,238,286
Number of options outstanding, Granted	892,500	51,120	900,084	92,600	943,620	992,684
Number of options outstanding, Exercised/issued						(5,692)
Number of options outstanding, Canceled/forfeited					(1,259,783)	(373,710)
Number of options outstanding, Ending balance					2,535,405	2,851,568
Weighted - average option exercise price
Weighted - average option exercise price, Beginning balance		$ 7.07			$ 7.07	$ 10.31
Weighted - average option exercise price, Granted					0.63	1.40
Weighted - average option exercise price, Exercised/issued						0.78
Weighted - average option exercise price, Canceled/forfeited					8.96	10.02
Weighted - average option exercise price, Ending balance					$ 3.73	$ 7.07
Number of restricted stock and board shares issued
Number of restricted stock shares issued, Beginning balance		201,455			201,455	140,653
Number of restricted stock shares issued, Granted					594,072	60,802
Number of restricted stock shares issued, Exercised/issued					0	0
Number of restricted stock shares issued, Canceled/forfeited					(30,701)
Number of restricted stock shares issued, Ending balance					764,826	201,455
Restricted Stock Units [Member]
Number of restricted stock units outstanding
Number of restricted stock units outstanding, Beginning balance		454,021			454,021	134,731
Number of restricted stock units outstanding, Granted						404,340
Number of restricted stock units outstanding, Exercised/issued					(133,685)	(29,432)
Number of restricted stock units outstanding, Canceled/forfeited					(194,497)	(55,618)
Number of restricted stock units outstanding, Ending balance					125,839	454,021