Federal and State Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Deferred Tax Assets, Gross [Abstract]
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost	$ 9,100,000	$ 10,100,000
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Credit loss allowances	86,100,000	102,700,000
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Valuation adjustments	45,100,000	42,300,000
Deferred Tax Assets, Deferred book income	7,200,000	9,200,000
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Deferred compensation	45,100,000	29,500,000
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Book expense in excess of pension contribution	400,000	1,900,000
Deferred Tax Assets, Other	30,900,000	38,500,000
Deferred Tax Assets, Gross	223,900,000	234,200,000
Deferred Tax Liabilities, Gross [Abstract]
Deferred Tax Liabilities, Available for sale securities	99,000,000	86,400,000
Deferred Tax Liabilities, Depreciation	19,600,000	29,400,000
Deferred Tax Liabilities, Mortgage servicing rights	59,500,000	48,900,000
Deferred Tax Liabilities, Lease financing	21,100,000	13,200,000
Deferred Tax Liabilities, Other	21,700,000	18,400,000
Deferred Tax Liabilities, Gross	220,900,000	196,300,000
Deferred Tax Assets, Net	3,000,000	37,900,000
Current Income Tax Expense [Abstract]
Components of Income Tax Expense, Current Income Tax Expense, Federal	159,706,000	137,802,000	132,165,000
Components of Income Tax Expense, Current Income Tax Expense, State	19,103,000	16,085,000	17,618,000
Components of Income Tax Epxnese, Current Income Tax Expense, Total	178,809,000	153,887,000	149,783,000
Deferred Income Tax Expense (Benefit) [Abstract]
Deferred Federal Income Tax Expense (Benefit)	8,664,000	3,882,000	(24,714,000)
Deferred State and Local Income Tax Expense (Benefit)	1,267,000	742,000	(1,712,000)
Deferred Income Tax Expense (Benefit)	9,931,000	4,624,000	(26,426,000)
Components of Income Tax Expense, Total income tax expense	188,740,000	158,511,000	123,357,000
Amount [Abstract]
Federal statutory tax	190,003,000	156,917,000	130,078,000
Tax exempt revenue	(5,558,000)	(5,357,000)	(5,404,000)
Effect of state income taxes, net of federal benefit	13,684,000	11,198,000	9,740,000
Utilization of tax credits	(5,126,000)	(2,972,000)	(6,317,000)
Bank-owned life insurance	(3,850,000)	(3,879,000)	(4,133,000)
Reduction of tax accrual	(950,000)	(1,764,000)	(2,245,000)
Other, net	537,000	4,368,000	1,638,000
Total	188,740,000	158,511,000	123,357,000
Percent of pretax income [Abstract]
Federal statutory tax (in hundredths)	35.00%	35.00%	35.00%
Tax exempt revenue (in hundredths)	(1.00%)	(1.00%)	(1.00%)
Effect of state income taxes, net of federal benefit (in hundredths)	3.00%	2.00%	3.00%
Utilization of tax credits (in hundredths)	(1.00%)	(1.00%)	(2.00%)
Bank-owned life insurance (in hundredths)	(1.00%)	(1.00%)	(1.00%)
Reduction of tax accrual (in hundredths)	0.00%	0.00%	(1.00%)
Other, net (in hundredths)	0.00%	1.00%	0.00%
Total (in hundredths)	35.00%	35.00%	33.00%
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits, Beginning Balance	12,230,000	11,900,000	12,300,000
Unrecognized Tax Benefits, Additions for Tax for Current Year Positions	3,976,000	6,390,000	3,700,000
Unrecognized Tax Benefits, Settlements During the Period	(1,000,000)	(2,510,000)	0
Unrecognized Tax Benefits, Lapse of Applicable Statute of Limitations	(2,931,000)	(3,550,000)	(4,100,000)
Unrecognized Tax Benefits, Ending Balance	12,275,000	12,230,000	11,900,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	1,200,000	1,900,000	1,300,000
Unrecognized Tax Benefits, Penalties and Interest Accrued	2,900,000	3,400,000
Unrecognized Tax Benefits, Number of Reporting Periods Open for Examination, Federal	3 years
Unrecognized Tax Benefits, Number of Reporting Periods Open for Examination, State, Minimum	3 years
Unrecognized Tax Benefits, Number of Reporting Periods Open for Examination, State, Maximum	6 years
Tax accrual reduction	$ 1,000,000	$ 1,800,000