Stockholders' Equity - Initial Public Offering and Follow-on Public Offering (Details) - Common Stock $ / shares in Units, $ in Millions		1 Months Ended		12 Months Ended
	May 02, 2014	Nov. 30, 2014 USD ($) $ / shares shares	May 31, 2014 USD ($) $ / shares shares	Dec. 31, 2014 shares
Class of Stock [Line Items]
Shares sold				8,941,250
Shares of common stock issued for conversion of series A preferred			2,857,143
Issuance of common stock in follow-on offering, net of underwriting discounts and offering costs (in shares)				1,960,390
IPO
Class of Stock [Line Items]
Shares sold			8,941,250
Public offering price (in dollars per share) | $ / shares			$ 9.00
Net proceeds | $			$ 69.2
Over-Allotment Option
Class of Stock [Line Items]
Shares sold			1,166,250
Follow On Public Offering
Class of Stock [Line Items]
Public offering price (in dollars per share) | $ / shares		$ 17.00
Issuance of common stock in follow-on offering, net of underwriting discounts and offering costs (in shares)		1,960,390
Shares sold		5,402,601
Net proceeds | $		$ 30.8
Conversion of convertible preferred stock
Class of Stock [Line Items]
Reverse split of common stock	0.6667