Income Taxes (Summary Of Income Tax Reconciliation) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Taxes [Abstract]
Federal income tax at expected statutory rate									$ 69,015	$ 65,429	$ 58,641
Tax-exempt interest, net of interest incurred to carry tax-exempt securities									(3,736)	(3,451)	(3,257)
Bank owned life insurance									(2,583)	(2,158)	(1,995)
State income tax expense (benefit), net of federal tax effect									12,727	629	(4)
Tax credits									(12,760)	(5,071)	(2,632)
Other, net									869	393	731
Income tax expense	$ 7,528	$ 13,696	$ 25,205	$ 17,103	$ 15,322	$ 14,168	$ 14,081	$ 12,200	$ 63,532	$ 55,771	$ 51,484