Premises and Equipment (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Premises and Equipment [Line Items]
Depreciation, depletion and amortization excluding intangibles	$ 22,900,000	$ 22,100,000	$ 19,500,000
Premises and Equipment, gross	461,569,000	443,611,000
Less accumulated depreciation and amortization	268,620,000	245,745,000
Premises and Equipment, net	192,949,000	197,866,000
Depreciation, Depletion and Amortization, Nonproduction	22,872,000	22,088,000	19,495,000
Land [Member]
Premises and Equipment [Line Items]
Premises and Equipment, gross	46,766,000	46,807,000
Estimated useful lives, Minimum	0
Estimated useful lives, Maximum	0
Buildings [Member]
Premises and Equipment [Line Items]
Premises and Equipment, gross	201,163,000	197,582,000
Estimated useful lives, Minimum	10
Estimated useful lives, Maximum	35
Equipment [Member]
Premises and Equipment [Line Items]
Premises and Equipment, gross	125,440,000	118,893,000
Estimated useful lives, Minimum	3
Estimated useful lives, Maximum	15
Leasehold improvements [Member]
Premises and Equipment [Line Items]
Premises and Equipment, gross	22,247,000	20,660,000
Estimated useful lives, Minimum	1
Estimated useful lives, Maximum	20
Software [Member]
Premises and Equipment [Line Items]
Premises and Equipment, gross	$ 65,953,000	$ 59,669,000
Estimated useful lives, Minimum	3
Estimated useful lives, Maximum	7