Stockholders' Equity (Details) (USD $)	0 Months Ended						12 Months Ended
	Apr. 30, 2014	Mar. 11, 2014	Jan. 15, 2014	Sep. 16, 2013	Feb. 22, 2013	Feb. 20, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Apr. 30, 2014	Mar. 11, 2014	Sep. 16, 2013	Mar. 29, 2012	Mar. 28, 2012
Stockholders' equity
Common Stock, par value (in dollars per share)							$ 0.01	$ 0.01
Common Stock, shares issued							173,644,532	106,356,558
Common Stock, Shares, Outstanding							173,266,416	106,190,652
Preferred Stock, Shares Authorized							5,000,000
Preferred Stock, Par or Stated Value Per Share							$ 0.01
Shares of common stock issued in an underwritten public offering	22,600,000	3,902,440	10,000,000	18,600,000		18,910,000
Per share price of shares of common stock sold in an underwritten public offering	$ 5.50	$ 5.74		$ 0.54						$ 5.50	$ 5.74	$ 0.54	$ 1.15	$ 1.15
Gross proceeds from shares of common stock sold in an underwritten public offering	$ 124,300,000	$ 22,400,006					$ 176,700,000
Net proceeds from shares of common stock sold	116,443,375	21,308,987		9,151,221	400,000		176,700,006	14,807,718	17,192,500
Warrants
Stockholders' equity
Increase in additional paid-in capital							$ 83,444,574
Series A Junior Participating Cumulative Preferred Stock
Stockholders' equity
Preferred Stock, Par or Stated Value Per Share								$ 0.01	$ 0.01
Shares, Outstanding								0	0