Convertible Preferred Stock Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2013
Class Of Stock [Line Items]
Number of securities issued upon exercise of warrants	158,179
Remeasurement of outstanding warrants	173,910
Warrants to purchase convertible preferred stock, exercise price	$ 5.17
Remeasurement [Member]
Class Of Stock [Line Items]
Expense related to change in fair value	$ 2,300
Reclassified to additional paid in capital	$ 2,800
IPO [Member]
Class Of Stock [Line Items]
Warrants to purchase convertible preferred stock, exercise price	$ 21.00
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