Employee Stock Purchase Plan Stock Options and Warrants Stock Option Activity (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value	$ 9,433	$ 1,928	$ 2,757
Employee Service Share-based Compensation, Cash Received from Exercise of Stock Options	7,197	1,330	1,690
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options	3,122	399	987
Stock Option Activity [Rollforward]
Stock Options Outstanding, Beginning of Period	4,389
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures	844	125	175
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	(1,099)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period	(57)
Stock Options Outstanding, End of Period	4,077	4,389
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	2,744
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	4,049
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 11.96	$ 10.56
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price	$ 13.75
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	$ 7.69
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price	$ 13
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 11.43
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$ 11.95
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	3.5
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	7,877
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	2.5
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	7,090
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term	3.5
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 5.28	$ 5.64	$ 5.49
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value	$ 7,871