Series C Convertible Preferred Stock Warrant Liability (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Oct. 31, 2013
Class of Warrant or Right [Line Items]
Proceeds from exercise of preferred stock warrants				$ 0	$ 8,150
Revaluation of convertible preferred stock warrant liability		$ 0	$ 127	$ 0	4,277
Warrants outstanding		0		0
Non-Operating Loss [Member]
Class of Warrant or Right [Line Items]
Revaluation of convertible preferred stock warrant liability			$ 127		$ 4,300
Convertible Preferred Stock, Series C [Member]
Class of Warrant or Right [Line Items]
Number of warrants exercisable (in shares)						1,975,532
Warrant exercise price (in USD per share)						$ 8.175
Warrants exercised in period (in shares)	996,940
Proceeds from exercise of preferred stock warrants	$ 8,100
Common Stock [Member]
Class of Warrant or Right [Line Items]
Warrants exercised in period (in shares)	978,592
Additional shares of common stock issued (in shares)	311,923