Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended					3 Months Ended
	Aug. 22, 2016	Jan. 31, 2017	Sep. 30, 2016	Aug. 31, 2016	Aug. 31, 2015	Jul. 31, 2015	Mar. 31, 2017	Dec. 31, 2016
Convertible Preferred Stock Warrants [Line Items]
Loss related to change in fair value							$ 15,231
Fair value of warrants							21,327	$ 2,723
2015 Placement Common Stock Warrants | Insiders
Convertible Preferred Stock Warrants [Line Items]
Warrants issued					198,760	198,760
Exercise price					$ 5.00	$ 5.00
Common stock warrants, expiry term					5 years	5 years
2016 Placement Warrant
Convertible Preferred Stock Warrants [Line Items]
Warrants issued			1,380,745	1,380,745
Exercise price			$ 2.95	$ 2.95
Common stock warrants, expiry term			7 years	7 years
Proceed from private placement and equity issuances, gross			$ 13,800				$ 13,800
Fair value of warrants upon issuance under Private Placement	$ 2,700
Expected term (in years)	7 years						6 years 4 months 24 days
Expected volatility	61.60%						67.90%
Risk-free interest rate	1.40%						2.20%
Expected dividend yield	0.00%						0.00%
Loss related to change in fair value							$ 6,800
Fair value of warrants							$ 9,500
2017 Placement Warrants Liability
Convertible Preferred Stock Warrants [Line Items]
Warrants issued		1,720,512
Exercise price		$ 3.17
Common stock warrants, expiry term		7 years
Proceed from private placement and equity issuances, gross		$ 26,100
Fair value of warrants upon issuance under Private Placement		$ 3,400
Expected term (in years)		7 years					6 years 9 months 18 days
Expected volatility		62.90%					67.90%
Risk-free interest rate		2.20%					2.20%
Expected dividend yield		0.00%					0.00%
Loss related to change in fair value							$ 8,400
Fair value of warrants							$ 11,800
Warrants exercisable term		6 months
Common Stock Warrant
Convertible Preferred Stock Warrants [Line Items]
Warrants issued							128,231	128,231
Exercise price							$ 5.84	$ 5.84
Common stock warrants, expiration date							Dec. 16, 2023