Share-Based Compensation (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Summary of stock option activity
Stock Options, Beginning balance			2,181,000
Stock option granted			0
Stock Options, Exercised	(912,000)
Stock option, Canceled	(24,000)
Stock Options, Ending balance	1,209,000		1,209,000
Stock Options, Exercisable	472,000		472,000
Stock Options, Vested and Expected to vest	1,191,000		1,191,000
Weighted-Average Exercise Price, Beginning balance			$ 17.20
Weighted-Average Exercise Price, Exercised	$ 16.82
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	$ 16.21
Weighted-Average Exercise Price, Ending balance	$ 17.11		$ 17.11
Weighted-Average Exercise Price, Exercisable	$ 16.69		$ 16.69
Weighted-Average Exercise Price, Vested and Expected to vest	$ 17.12		$ 17.12
Summary of nonvested stock activity
Shares, Beginning balance			1,451,000
Shares, Granted			12,052
Shares, Vested			(362,000)
Shares, Ending balance	1,101,000		1,101,000
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			$ 20.25
Grant Date Weighted-Average Fair Value Per Share, Ending balance	$ 19.84		$ 19.84
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	$ 12,100,000		$ 12,100,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition			2 years 110 days
Allocated Share-based Compensation Expense	1,800,000	2,100,000	6,700,000	9,100,000
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	4,100,000		4,100,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition			2 years 146 days
Allocated Share-based Compensation Expense	$ 436,000	$ 362,000	$ 1,500,000	$ 1,100,000