Shareholders' Equity (Narrative) (Details) (USD $)	3 Months Ended			12 Months Ended
	Mar. 31, 2011	Mar. 31, 2009	Mar. 31, 2008	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock raised through a public offer						$ 89,786,000
Redeemed fixed rate cumulative perpetual preferred stock						214,181,000
Repurchase of warrants issued to U.S. Treasury						4,500,000
Common stock, shares authorized				200,000,000	200,000,000
Vesting period of stock awards				5 years
Compensation cost				4,041,000	3,785,000	3,505,000
Income tax benefits received				1,200,000	694,000	406,000
Tax deficiency from stock options exercised				59,000	261,000	216,000
2007 Long Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock unit grants, authorized				1,000,000
2003 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock unit grants, authorized				4,000,000
Grants issued on diluted common stock shares maximum percentage				10.00%
Maximum term of award				10 years
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost				1,100,000	1,200,000	861,000
Total income tax benefit recognized related to stock-based compensation				448,000	463,000	344,000
Total intrinsic value of options outstanding				749,000
Total intrinsic value of options exercisable				404,000
Weighted average remaining contractual term of options exercisable				3 years 10 months 24 days
Total intrinsic value of options exercised				1,200,000	147,000	420,000
Cash received from exercise of stock options				981,000	309,000	1,000,000
Stock repurchase program number of shares tendered				37,720	8,135
Nonvested Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost related to nonvested stock awards				1,600,000
Expected recognized over a weighted-average period, years				1 year 7 months 6 days
Restricted Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of stock awards				3 years
Period of time after separation when vested award certificates are issued				7 months
Compensation cost				2,700,000	2,300,000	1,900,000
Total income tax benefit recognized related to stock-based compensation				1,100,000	899,000	746,000
Restricted stock share based compensation arrangement by share based payment award, award vesting period				5 years
Restricted stock units at fair value				1,900,000	919,000	571,000
Total unrecognized compensation cost related to nonvested stock awards				4,800,000
Expected recognized over a weighted-average period, years				1 year 10 months 24 days
Stock units granted to executives that cliff vest, years	3 years	3 years	3 years
Cancellation of restricted stock shares to pay withholding				45,873	23,158
Restricted Stock Units (RSU's) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost				237,000	391,000	778,000
Total income tax benefit recognized related to stock-based compensation				95,000	156,000	311,000
Total fair value of restricted stock shares/units vested and released					677,000	213,000
Total unrecognized compensation cost related to nonvested stock awards				$ 549,000
Expected recognized over a weighted-average period, years				1 year 3 months 18 days
Stock units granted to executives that cliff vest, years		3 years	4 years
Cancellation of restricted stock units to pay withholding					22,439
Stock Repurchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase plan, amended authorized shares				15,000,000
Share repurchase plan, shares remained available for repurchase				12,100,000
Shares under the repurchase plan				512,280	2,500,000	0
Minimum [Member] | 2003 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of stock awards				3 years
Maximum [Member] | 2003 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of stock awards				5 years