Federal and State Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets [Abstract]
Credit loss reserves	$ 50,611	$ 49,804
Lease liability	46,084	0
Deferred compensation	25,976	25,608
Purchased loan discount	18,042	27,283
Unearned fees	9,080	9,814
Share-based compensation	7,392	4,434
Valuation adjustments	1,545	9,619
Available for sale securities mark to market	0	24,441
Other	26,384	31,489
Total deferred tax assets	185,114	182,492
Valuation Allowance [Abstract]
Valuation allowance	0	0
Deferred tax liabilities [Abstract]
Mortgage servicing rights	48,435	61,844
Right-of-use asset	42,180	0
Available for sale securities mark to market	33,140	0
Acquired identifiable intangible	23,181	28,620
Depreciation	18,909	15,966
Lease financing	10,720	10,040
Other	34,826	30,566
Total deferred tax liabilities	211,391	147,036
Net deferred tax assets, net	26,277	35,456
Current income tax expense [Abstract]
Federal	110,887	103,748	$ 141,607
State	15,088	15,253	14,592
Total current income tax expense	125,975	119,001	156,199
Deferred income tax expense [Abstract]
Federal	3,416	(190)	25,525
State	792	250	869
Total deferred income tax expense	4,208	60	26,394
Total income tax expense	130,183	119,061	182,593
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Federal statutory tax	132,482	118,752	181,397
Tax exempt revenue	(12,227)	(8,311)	(12,402)
Effect of state income taxes, net of federal benefit	12,715	12,430	10,701
Utilization of tax credits, net of proportional amortization of low-income housing limited partnership investments	(5,127)	(4,559)	(6,811)
Other, net	2,340	749	9,708
Total income tax expense	$ 130,183	$ 119,061	$ 182,593
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory tax (in thousandths)	21.00%	21.00%	35.00%
Tax exempt revenue (in thousandths)	(1.90%)	(1.50%)	(2.40%)
Effect of state income taxes, net of federal benefit (in thousandths)	2.00%	2.20%	2.00%
Utilization of tax credits, net of proportional amortization of low-income housing limited partnership investments (in thousandths)	(0.80%)	(0.80%)	(1.30%)
Other, net (in thousandths)	0.30%	0.20%	1.90%
Total (in thousandths)	20.60%	21.10%	35.20%
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of January 1	$ 18,869	$ 18,110	$ 15,841
Additions for tax for current year positions	5,649	2,649	4,645
Settlements during the period	0	0	0
Lapses of applicable statute of limitations	(4,053)	(1,890)	(2,376)
Balance as of December 31	20,465	18,869	18,110
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	14,700
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	2,200	1,700	$ 1,200
Unrecognized Tax Benefits, Penalties and Interest Accrued	$ 5,600	$ 5,000
Unrecognized Tax Benefits, Number of Reporting Periods Open for Examination, Federal	3
Unrecognized Tax Benefits, Number of Reporting Periods Open for Examination, State, Minimum	3
Unrecognized Tax Benefits, Number of Reporting Periods Open for Examination, State, Maximum	6