Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended			3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Aug. 22, 2016	Sep. 30, 2016	Aug. 31, 2015	Jul. 31, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Sep. 09, 2016
Convertible Preferred Stock Warrants [Line Items]
Convertible preferred stock warrant liability	$ 158							$ 93
Change in the fair value of the warrant							$ (6)	(1,646)	$ 45
Loss related to change in fair value								1,646
Fair value of warrants	4,372		$ 4,372			$ 4,372		4,372
2015 Private Placement Common Stock Warrants
Convertible Preferred Stock Warrants [Line Items]
Estimated fair value of the warrants issued to placement agents	$ 316		$ 316			$ 316		$ 316
Warrant exercised								0		0
Expected term (in years)								5 years
Expected volatility								31.80%
Risk-free interest rate								1.60%
Expected dividend yield								0.00%
2015 Private Placement Common Stock Warrants | Insiders
Convertible Preferred Stock Warrants [Line Items]
Warrants issued				198,760	198,760
Warrants exercise per share				$ 5.00	$ 5.00
Common stock warrants, expiry term				5 years	5 years
2016 Placement Warrants
Convertible Preferred Stock Warrants [Line Items]
Warrants issued	1,380,745	1,380,745	1,380,745			1,380,745		1,380,745			1,380,745
Warrants exercise per share	$ 2.95	$ 2.95	$ 2.95			$ 2.95		$ 2.95
Common stock warrants, expiry term		7 years	7 years
Gross proceeds from Issuance of Private Placement								$ 13,750
Fair value of warrants upon issuance under Private Placement		$ 2,700
Expected term (in years)		7 years						6 years 10 months 24 days
Expected volatility		61.60%						64.30%
Risk-free interest rate								1.40%
Expected dividend yield								0.00%
Loss related to change in fair value						$ (1,600)		$ (1,600)
Fair value of warrants	$ 4,400		$ 4,400			4,400		$ 4,400
Hercules Term Loan
Convertible Preferred Stock Warrants [Line Items]
Expected term (in years)								2 years
Expected volatility								30.00%
Risk-free interest rate								0.40%
Expected dividend yield								0.00%
Fair value of warrants	$ 158		$ 158			$ 158		$ 158
Hercules Term Loan | Series C Convertible Preferred Stock
Convertible Preferred Stock Warrants [Line Items]
Warrants issued	128,231		128,231		128,231	128,231		128,231