Preferred Stock Warrants - Summary of Convertible Preferred Stock Warrants (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Jul. 21, 2015	Dec. 31, 2014	Dec. 31, 2013
Class of Warrant or Right [Line Items]
Preferred stock warrants outstanding			975,335	998,249
Preferred stock warrants exercise price		$ 17.00
Series A Convertible Preferred Stock [Member]
Class of Warrant or Right [Line Items]
Preferred stock warrants outstanding				22,914
Preferred stock warrants exercise price			$ 11.324
Preferred stock warrants expiration date, description	Various dates in 2014
Series B Redeemable Convertible Preferred Stock [Member]
Class of Warrant or Right [Line Items]
Preferred stock warrants outstanding			10,414	10,414
Preferred stock warrants exercise price			$ 7.45
Preferred stock warrants expiration date	Jul. 31, 2018
Series C Redeemable Convertible Preferred Stock [Member]
Class of Warrant or Right [Line Items]
Preferred stock warrants outstanding			171,566	171,566
Preferred stock warrants exercise price			$ 5.125
Preferred stock warrants expiration date, description	Various dates in 2022 - 2023
Series B-1 Redeemable Convertible Preferred Stock Warrants At Exercise Price Of $7.45 [Member]
Class of Warrant or Right [Line Items]
Preferred stock warrants outstanding			47,060	47,060
Preferred stock warrants exercise price			$ 7.45
Preferred stock warrants expiration date	Jun. 30, 2018
Series B-1 Redeemable Convertible Preferred Stock Warrants At Exercise Price Of $2.6075 [Member]
Class of Warrant or Right [Line Items]
Preferred stock warrants outstanding			746,295	746,295
Preferred stock warrants exercise price			$ 2.6075
Preferred stock warrants expiration date, description	Various dates in 2016 - 2021