Convertible Preferred Stock Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2014	Dec. 31, 2013
Class Of Stock [Line Items]
Number of securities issued upon exercise of warrants	158,179	158,179
Remeasurement of outstanding warrants	173,910
Warrants to purchase convertible preferred stock, exercise price	$ 5.17	$ 5.17
Reclassification of warrant liability		$ 2,300
IPO [Member]
Class Of Stock [Line Items]
Warrants to purchase convertible preferred stock, exercise price	$ 21.00	$ 21.00
Reclassification of warrant liability				$ 2,752
IPO [Member] | Additional Paid-in Capital [Member]
Class Of Stock [Line Items]
Reclassification of warrant liability	$ 2,800			$ 2,752
2012 Notes [Member]
Class Of Stock [Line Items]
Percentage of shares issuable on conversion of debt as warrants			20.00%
Warrants term			5 years
Warrants expiration date			Oct. 12, 2017
Fair value of warrants			$ 433		$ 474
Risk-free interest rate			0.21%
Expected volatility			90.00%
Expected term (in years)			1 year 6 months