Premises and Equipment (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Premises and Equipment
Cost	$ 456,531,000	$ 415,049,000
Accumulated Depreciation And Amortization	312,890,000	286,623,000
Carrying Value	143,641,000	128,426,000
Depreciation and amortization	27,596,000	25,845,000	26,219,000
Net rental payments on operating leases	45,400,000	46,500,000	43,200,000
Premises, including land
Premises and Equipment
Cost	153,578,000	143,658,000
Accumulated Depreciation And Amortization	97,906,000	89,931,000
Carrying Value	55,672,000	53,727,000
Range of Lives, maximum (in years)	39	39
Land	3,511,000	3,511,000
Furniture, fixtures and equipment
Premises and Equipment
Cost	183,186,000	171,642,000
Accumulated Depreciation And Amortization	146,762,000	137,798,000
Carrying Value	36,424,000	33,844,000
Range of Lives, minimum (in years)	3	3
Range of Lives, maximum (in years)	10	10
Software
Premises and Equipment
Cost	119,767,000	99,749,000
Accumulated Depreciation And Amortization	68,222,000	58,894,000
Carrying Value	$ 51,545,000	$ 40,855,000
Range of Lives (in years)	5	5