Net Loss Per Common Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from the computation of earnings per share (in shares)	7,728,775	4,971,423	7,896,343	3,643,286
Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from the computation of earnings per share (in shares)	6,422,034	1,386,888	4,328,089	984,127
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from the computation of earnings per share (in shares)	1,206,504	3,525,872	3,469,612	2,621,450
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from the computation of earnings per share (in shares)	100,237	58,663	98,642	37,709