Federal and State Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets [Abstract]
Available for sale securities mark to market	$ 154,277	$ 183,723
Credit loss reserves	78,016	76,361
Lease liability	58,399	61,204
Deferred compensation	51,545	47,418
Unearned fees	13,268	12,682
Other	25,918	29,193
Total deferred tax assets	381,423	410,581
Valuation Allowance [Abstract]
Valuation allowance	0	0
Deferred tax liabilities [Abstract]
Right-of-use asset	49,249	51,943
Mortgage servicing rights	35,464	32,723
Acquired identifiable intangible	20,619	21,678
Depreciation	5,878	4,578
Lease financing	9,342	12,148
Other	29,002	17,915
Total deferred tax liabilities	149,554	140,985
Net deferred tax assets, net	231,869	269,596
Current income tax expense [Abstract]
Federal	116,663	152,600	$ 127,144
State	18,148	19,298	18,185
Total current income tax expense	134,811	171,898	145,329
Deferred income tax expense [Abstract]
Federal	7,632	(17,973)	(4,700)
State	648	(1,810)	(765)
Total deferred income tax expense (benefit)	8,280	(19,783)	(5,465)
Total income tax expense	143,091	152,115	139,864
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Federal statutory tax	139,996	143,482	138,633
Tax exempt revenue	(6,341)	(5,786)	(5,714)
State income taxes, net of federal benefit	15,055	13,330	13,490
Tax credits, net of proportional amortization	(8,857)	(2,673)	(8,883)
Other, net	3,238	3,762	2,338
Total income tax expense	$ 143,091	$ 152,115	$ 139,864
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory tax (in thousandths)	21.00%	21.00%	21.00%
Tax exempt revenue (in thousandths)	(1.00%)	(0.80%)	(0.80%)
Effect of state income taxes, net of federal benefit (in thousandths)	2.30%	2.00%	2.00%
Utilization of tax credits, net of proportional amortization of low-income housing limited partnership investments (in thousandths)	(1.30%)	(0.40%)	(1.40%)
Other, net (in thousandths)	0.50%	0.50%	0.40%
Total (in thousandths)	21.50%	22.30%	21.20%
Unrecognized Tax Benefits [Roll Forward]
Balance as of January 1	$ 17,957	$ 19,583	$ 21,092
Additions for tax for current year positions	3,397	3,239	3,465
Lapses of applicable statute of limitations	(4,855)	(4,865)	(4,974)
Balance as of December 31	16,499	17,957	19,583
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	13,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	1,600	1,600	$ 1,800
Unrecognized Tax Benefits, Penalties and Interest Accrued	$ 5,000	$ 5,700
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