Share-Based Compensation (Details 3) (Performance Shares [Member], USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2009
Performance Shares [Member]
Nonvested performance shares
Weighted number of shares, Nonvested, Beginning Balance	672,000
Weighted Average Grant Date Fair Value, Beginning of Period	$ 12.23
Number of Shares, Granted	227,000	350,248
Weighted Average Grant Date Fair Value, Nonvested, Granted	$ 25.40
Number of Shares Vested	293,299
Vested, weighted average Grant Date Fair Value	$ 8.94
Number Of Shares Forfeited	(166,000)
Forfeited, Weighted Average Grant Date Fair Value	$ 17.30
Weighted number of shares , Nonvested, Ending Balance	440,000
Weighted Average Grant Date Fair Value, Ending of Period	$ 19.32