Share-Based Compensation (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Summary of stock option activity
Stock Options, Beginning balance			2,181,000
Stock option granted			0
Stock Options, Exercised	(270,000)
Stock option, Canceled	(23,000)
Stock Options, Ending balance	1,852,000		1,852,000
Stock Options, Exercisable	777,000		777,000
Stock Options, Vested and Expected to vest	1,825,000		1,825,000
Weighted-Average Exercise Price, Beginning balance			$ 17.20
Weighted-Average Exercise Price, Exercised	$ 16.34
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period	36,000
Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price			$ 30.70
Weighted-Average Exercise Price, Canceled	$ 16.16
Weighted-Average Exercise Price, Ending balance	$ 17.08		$ 17.08
Weighted-Average Exercise Price, Exercisable	$ 16.84		$ 16.84
Weighted-Average Exercise Price, Vested and Expected to vest	$ 17.10		$ 17.10
Summary of nonvested stock activity
Shares, Beginning balance			1,451,000
Shares, Granted			12,052
Shares, Vested			(290,000)
Shares, Forfeited/Canceled			0
Shares, Ending balance	1,173,000		1,173,000
Grant Date Weighted-Average Fair Value Per Share, Beginning balance			$ 19.90
Grant Date Weighted-Average Fair Value Per Share, Granted			$ 24.89
Grant Date Weighted-Average Fair Value Per Share, Vested			$ 20.45
Grant Date Weighted-Average Fair Value Per Share, Forfeited/Canceled			$ 0.00
Grant Date Weighted-Average Fair Value Per Share, Ending balance	$ 19.82		$ 19.82
Nonvested Stock Awards [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$ 13,900,000		$ 13,900,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition			2 years 176 days
Allocated Share-based Compensation Expense	2,400,000	3,300,000	5,000,000	7,000,000
Summary of nonvested stock activity
Shares, Granted			12,000
Employee Stock Option [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	4,500,000		4,500,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition			2 years 256 days
Allocated Share-based Compensation Expense	$ 490,000	$ 269,000	$ 1,100,000	$ 744,000