Stock Based Compensation (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of nonvested stock activity
Granted, Shares	3,060,519	1,624,369	1,348,474
Nonvested Stock Options [Member]
Summary of nonvested stock activity
Stock Options Shares Outstanding, Beginning balance	2,431,339	2,025,720	1,896,992
Granted, Shares	3,060,519	1,624,369	1,348,474
Vested, Shares	(1,097,571)	(955,454)	(920,969)
Forfeited, Shares	(357,692)	(263,296)	(298,777)
Stock Options Shares Outstanding, Ending balance	4,036,595	2,431,339	2,025,720
Nonvested Weighted Average Grant Date Fair Value, Beginning balance	5.11	4.09	3.60
Granted Weighted Average Grant Date Fair Value	5.03	5.56	4.60
Vested Weighted Average Grant Date Fair Value	4.88	3.77	3.93
Forfeited Weighted Average Grant Date Fair Value	5.12	4.85	3.78
Nonvested Weighted Average Grant Date Fair Value, Ending balance	5.11	5.11	4.09