Subsequent Event (Details) - USD ($) $ / shares in Units, $ in Millions				1 Months Ended
	Apr. 12, 2017	Apr. 05, 2017	Apr. 03, 2017	Apr. 30, 2017	Apr. 04, 2017	Mar. 31, 2017	Dec. 31, 2016	Jan. 31, 2014
Subsequent Events
Proceeds from Issuance of Warrants	$ 15.8
Common Stock, par value (in dollars per share)						$ 0.01	$ 0.01
Series D Redeemable Convertible Preferred Stock
Subsequent Events
Shares of common stock that can be purchased from warrants issued in an underwritten public offering (in shares)							7,381,500
Warrants issued in January, 2014
Subsequent Events
Exercise price of warrants (in dollars per share)								$ 4.00
Warrants issued in December 2016
Subsequent Events
Exercise price of warrants (in dollars per share)							$ 1.50
Subsequent event
Subsequent Events
Exercise price of warrants (in dollars per share)	$ 2.69
Shares of common stock that can be purchased from warrants issued in an underwritten public offering (in shares)	5,250,750				55,286,696
Common Stock, par value (in dollars per share)			$ 0.01
Aggregate offering price			$ 75.0
Stock Issued During Period, Shares, New Issues			8,067,152
Net proceeds			$ 18.2
Subsequent event | Series D Redeemable Convertible Preferred Stock
Subsequent Events
Shares issued result of exercise of warrants (in shares)		9,548,393
Exercise price of warrants (in dollars per share)		$ 1.55
Subsequent event | Warrants issued in January, 2014
Subsequent Events
Shares issued result of exercise of warrants (in shares)				4,000,000
Exercise price of warrants (in dollars per share)				$ 0.65
Subsequent event | Warrants issued in December 2016
Subsequent Events
Shares issued result of exercise of warrants (in shares)	10,501,500
Exercise price of warrants (in dollars per share)	$ 1.50