Stockholders' Equity (Summary of Status of Nonvested Shares) (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Number of Options
Nonvested Shares at December 31, 2014			6,032,315
Granted			738,250
Vested			(767,322)
Cancelled or expired			(926,578)
Nonvested Shares at June 30, 2015	5,076,665		5,076,665
Weighted Average Grant- Date Fair Value (usd per share)
Nonvested Shares at December 31, 2014			$ 5.66
Granted	$ 4.20	$ 4.76	4.54	$ 5.06
Vested			2.85
Cancelled or expired			6.04
Nonvested Shares at June 30, 2015	$ 5.54		$ 5.54