Stockholders' Equity - Common Stock and Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jan. 31, 2014	Dec. 31, 2013	Feb. 28, 2013
Stockholders' equity
Common Stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Common Stock, Shares, Outstanding	191,141,646	191,141,646	180,087,491
Shares of common stock issuances	10,400,000			36,502,440
Shares of common stock that can be purchased from warrants issued in an underwritten public offering (in shares)	3,120,000	3,120,000
Shares of common stock sold in an underwritten public offering (in shares)				26,502,440
Net proceeds from public offering	$ 11,900	$ 27,500		$ 165,700
Proceeds from Issuance of Warrants				$ 11,800
Common stock shares callable per warrant	1	1
Exercise price of warrants (in dollars per share)	$ 1.50	$ 1.50
Number of warrants exercised (in shares)		119,879	26,882	23,918,429
Shares issued result of exercise of warrants (in shares)		119,879	26,882	23,832,038
Proceeds from exercise of warrants		$ 111	$ 25	$ 18,340
Increase in Paid-in capital and reduction of warrant liability		$ 141	$ 22	$ 83,400
Warrants outstanding (in shares)	14,501,600	14,501,600	4,192,567
Minimum
Stockholders' equity
Per share price of shares of common stock sold in an underwritten public offering (in dollars per share)				$ 5.50
Maximum
Stockholders' equity
Per share price of shares of common stock sold in an underwritten public offering (in dollars per share)				$ 5.74
Underwriters agreement
Stockholders' equity
Shares of common stock that can be purchased from warrants issued in an underwritten public offering (in shares)	7,381,500	7,381,500
Warrants issued in February, 2013
Stockholders' equity
Exercise price of warrants (in dollars per share)							$ 0.15
Warrants outstanding (in shares)	100	100	100	100
Warrants issued in February, 2013 | Minimum
Stockholders' equity
Exercise price of warrants (in dollars per share)						$ 0.15
Warrants issued in January, 2014
Stockholders' equity
Shares of common stock that can be purchased from warrants issued in an underwritten public offering (in shares)				4,000,000
Number of shares of common stock in each fixed combination of shares and the warrants sold (in shares)				1
Number of warrants in each fixed combination of shares and the warrants sold to purchase one share of common stock (in shares)				0.40
Price of per fixed combination of the shares and the warrants sold (in dollars per share)				$ 3.00
Number of share sold in a fixed combination of shares and warrants (in shares)				10,000,000
Exercise price of warrants (in dollars per share)	$ 1.025	$ 1.025		$ 4.00	$ 4.00
Number of warrants exercised (in shares)		0	0	0
Warrants issued in December 2016
Stockholders' equity
Exercise price of warrants (in dollars per share)	$ 1.50	$ 1.50
Number of warrants exercised (in shares)		0