Stockholders' Equity - Common Stock and Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stockholders' equity
Common Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, Shares, Outstanding	180,087,491	173,266,416
Shares of common stock issuances		36,502,440	43,101,800
Per share price of shares of common stock sold in an underwritten public offering (in dollars per share)			$ 0.54
Shares of common stock sold in an underwritten public offering (in shares)		26,502,440	21,390,000
Shares of common stock that can be purchased from warrants issued in an underwritten public offering (in shares)		4,000,000	21,711,800
Number of shares of common stock in each fixed combination of shares and the warrants sold (in shares)		1	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	1
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
Net proceeds from public offering		$ 165,700	$ 12,900
Proceeds from Issuance of Warrants		$ 11,800	$ 2,500
Exercise price of warrants (in dollars per share)		$ 4.00
Number of warrants exercised (in shares)	26,882	23,918,429	22,494,987
Shares issued result of exercise of warrants (in shares)	26,882	23,832,038	22,494,987
Proceeds from exercise of warrants	$ 25	$ 18,340	$ 6,103
Increase in Paid-in capital and reduction of warrant liability	$ 22	$ 83,400	$ 11,200
Warrants outstanding (in shares)	4,192,567	4,219,449
Minimum
Stockholders' equity
Per share price of shares of common stock sold in an underwritten public offering (in dollars per share)		$ 5.50
Price of per fixed combination of the shares and the warrants sold (in dollars per share)			$ 0.15
Exercise price of warrants (in dollars per share)			0.15
Maximum
Stockholders' equity
Per share price of shares of common stock sold in an underwritten public offering (in dollars per share)		$ 5.74
Price of per fixed combination of the shares and the warrants sold (in dollars per share)			0.18
Exercise price of warrants (in dollars per share)			$ 0.18