Common Stock and Stockholders' Equity (Deficit) - Temporary Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	Jul. 07, 2015	Jun. 17, 2015	Dec. 31, 2014	Dec. 31, 2013
Temporary equity
Number of shares issued upon conversion of convertible stock	25,500,000
Temporary equity, shares outstanding			50,452,939
Convertible Preferred Stock
Temporary equity
Share price threshold of initial public offering for automatic conversion into common stock (in dollars per share)		$ 12.00
Threshold of proceeds from initial public offering for automatic conversion into common stock		$ 75,000
Number of shares issued upon conversion of convertible stock	25,500,000
Temporary equity, shares outstanding			50,452,939	37,590,286
Temporary equity, carrying amount			$ 117,914	$ 71,655
Redeemable Common Stock
Temporary equity
Number of shares issued upon conversion of convertible stock	113,294
Temporary equity, shares outstanding			113,294	113,294
Temporary equity, carrying amount			$ 2,852	$ 2,852