Stockholders' Equity - Initial Public Offering and Related Transactions (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	May. 29, 2014	Dec. 31, 2014
Convertible notes | Convertible Promissory Notes, April 2014
Stockholders' equity
Conversion to common stock	$ 3,000	$ 3,020
Redeemable Convertible Preferred Stock
Stockholders' equity
Conversion to common stock		$ 69,233
Common stock | Convertible notes | Convertible Promissory Notes, April 2014
Stockholders' equity
Conversion to common stock (in shares)	503,450	503,450
Common stock | Redeemable Convertible Preferred Stock
Stockholders' equity
Conversion to common stock		$ 1
Conversion to common stock (in shares)	8,809,325	8,803,547
Initial public offering
Stockholders' equity
Proceeds from the issuance of common stock, net	$ 49,700
Initial public offering | Common stock
Stockholders' equity
Common stock issued (in shares)	9,166,667	9,166,667
Share price (in dollars per share)	$ 6.00