Stock-Based Compensation (Summary of Option Activity) (Details) (USD $)	6 Months Ended
	Jun. 30, 2013
2005 Stock Incentive Plan [Member]
Stock Options
Outstanding at January 1, 2013	9,143,825
Granted	4,007,500
Exercised	(133,917)
Canceled	(750,008)
Outstanding at June 30, 2013	12,267,400
Shares exercisable at June 30, 2013	4,662,956
Shares available for grant at June 30, 2013	2,518,619
Weighted-Average Exercise Price
Outstanding at January 1, 2013	$ 1.87
Granted	$ 1.89
Exercised	$ 2.02
Canceled	$ 1.72
Outstanding at June 30, 2013	$ 1.88
Options exercisable, June 30, 2013	$ 2.17
1995 Stock Option Plan [Member]
Stock Options
Outstanding at January 1, 2013	211,900
Granted
Exercised
Canceled	(23,750)
Outstanding at June 30, 2013	188,150
Shares exercisable at June 30, 2013	188,150
Weighted-Average Exercise Price
Outstanding at January 1, 2013	$ 4.94
Granted
Exercised
Canceled	$ 4.05
Outstanding at June 30, 2013	$ 5.04
Options exercisable, June 30, 2013	$ 5.04