Preferred Stock Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		9 Months Ended	12 Months Ended
	Jul. 21, 2015	Sep. 30, 2015	Dec. 31, 2015
Class of Warrant or Right [Line Items]
Fair value of warrant liability reclassified to redeemable convertible preferred stock and additional paid-in capital			$ 19,300
Warrants exercised	493,648
Warrants exercise price	$ 17.00
Cash proceeds from warrants exercised		$ 1,507	$ 1,500
Number of common stock shares issued upon exercise of preferred stock warrants	390,680		481,671
Series B Redeemable Convertible Preferred Stock [Member]
Class of Warrant or Right [Line Items]
Warrants exercised	10,414
Number of common stock shares issued upon exercise of preferred stock warrants	6,499
Series B-1 Redeemable Convertible Preferred Stock [Member]
Class of Warrant or Right [Line Items]
Warrants exercised	349,054
Number of common stock shares issued upon exercise of preferred stock warrants	291,164		444,286
Series C Redeemable Convertible Preferred Stock [Member]
Class of Warrant or Right [Line Items]
Warrants exercised	134,180
Number of common stock shares issued upon exercise of preferred stock warrants	93,017		37,385
Series B-1 Redeemable Convertible Preferred Stock Cash Exercised at Exercise Price of $7.45 [Member]
Class of Warrant or Right [Line Items]
Warrants exercised			31,778
Warrants exercise price			$ 7.45
Series B-1 Redeemable Convertible Preferred Stock Warrants Cash Exercised at Exercise Price of $2.6075 [Member]
Class of Warrant or Right [Line Items]
Warrants exercised			412,508
Warrants exercise price			$ 2.6075
Series C Redeemable Convertible Preferred Stock Warrants Cash Exercised at Exercise Price of $5.215 [Member]
Class of Warrant or Right [Line Items]
Warrants exercised			37,385
Warrants exercise price			$ 5.215