Preferred Stock Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Class of Warrant or Right [Line Items]
Preferred stock warrant liabilities	$ 10,641	$ 10,641	$ 1,810
Warrants exercised			0
Cash proceeds from warrants exercised		300
Fair value of warrant liability reclassified to redeemable convertible preferred stock		$ 1,100
Series B-1 Preferred Stock Warrants, Expiration June 30, 2018 [Member]
Class of Warrant or Right [Line Items]
Warrants exercised	3,079	3,079
Warrants exercise price	$ 7.4500	$ 7.4500
Series B-1 Preferred Stock Warrants, Expiration Various Dates In 2016 - 2021 [Member]
Class of Warrant or Right [Line Items]
Warrants exercised	82,949	82,949
Warrants exercise price	$ 2.6075	$ 2.6075
Series C Preferred Stock Warrants [Member]
Class of Warrant or Right [Line Items]
Warrants exercised	5,247	5,247
Warrants exercise price	$ 5.2150	$ 5.2150