Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract]
Net Income (Loss)	$ 119,635	$ 101,687
Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract]
Provision for Loan, Lease, and Other Losses	11,001	13,003
Depreciation	12,214	13,981
Mortgage Servicing Rights (MSR) Impairment (Recovery)	(1,261)	1,047
Amortization of Intangible Assets	2,203	2,203
Accretion (Amortization) of Discounts and Premiums, Investments	12,264	6,336
Other Depreciation and Amortization	8,455	8,689
Marketable Securities, Gain (Loss)	4	0
Gain (Loss) on Disposition of Assets	(840)	878
(Gain) loss on mortgage banking activities, net	998	329
Gain (Loss) on Sale of Mortgage Loans	0	6,976
Increase (Decrease) in Obligation, Pension Benefits	(8,206)	(6,186)
Payment for Origination and Purchase, Loan, Held-for-Sale	(159,442)	(92,584)
Proceeds from Sale, Loan, Mortgage, Held-for-Sale	146,457	105,642
Increase (Decrease) in Other Operating Assets and Liabilities, Net [Abstract]
Increase (Decrease) in Accrued Interest Receivable, Net	97	8,044
Decrease in net income tax position	22,342	29,846
Increase (Decrease) in Interest Payable, Net	1,409	(2,025)
Increase (Decrease) in Other Accounts Payable and Accrued Liabilities	(52,852)	(53,261)
Increase (Decrease) in Derivative Assets and Liabilities	3,169	(36,128)
Increase (Decrease) in Other Noncurrent Assets	(3,816)	(5,204)
Increase (Decrease) in Other Operating Assets and Liabilities, Net	22,034	(5,107)
Net Cash Provided by (Used in) Operating Activities, Total	135,865	98,166
Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract]
Payments for (Proceeds from) Loans and Leases	(656,118)	(513,237)
Payment for Investing Activity [Abstract]
Payments to Acquire Debt Securities, Available-for-Sale	(534,565)	(391,952)
Payments to Acquire Held-to-Maturity Securities	0	(994)
Payments to Acquire Federal Home Loan Bank Stock	(56,881)	(71,364)
Proceeds from Investing Activity [Abstract]
Proceeds from Sale of Held-to-Maturity Securities	1,222	0
Proceeds from Sale of Federal Home Loan Bank Stock	19,206	56,786
Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-Sale	380,404	206,882
Proceeds from Maturities, Prepayments and Calls of Held-to-Maturity Securities	31,062	34,673
Proceeds from Sale and Maturity of Other Investments	3,734	2,631
Proceeds from Sale of Mortgage Portfolio	0	564,375
Payments for (Proceeds from) Productive Assets	(8,701)	(7,472)
Net Change in Tax Credit Investments	(3,543)	(7,448)
Net Cash Provided by (Used in) Investing Activities, Total	(824,180)	(127,119)
Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract]
Increase (Decrease) in Deposits	179,157	548,279
Proceeds from (Repayments of) Short-Term Debt	87,788	(159,033)
Increase (Decrease) in Loans from Federal Home Loan Banks	154,750	170,000
Payments of FHLBank Borrowings, Financing Activities	(33)	(32)
Finance Lease, Principal Payments	0	(22)
Repayments of Senior Debt	0	(250,000)
Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Including Option Exercised	7,121	2,192
Payments of Ordinary Dividends, Common Stock	(40,058)	(38,538)
Payments of Ordinary Dividends, Preferred Stock and Preference Stock	(2,875)	(2,875)
Proceeds from (Payment for) Other Financing Activity	0	(52)
Net Cash Provided by (Used in) Financing Activities, Total	354,271	241,810
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect, Total	(334,044)	212,856
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Beginning Balance	1,720,221	1,019,604	$ 1,019,604
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Ending Balance	1,386,177	1,232,460	1,720,221
Supplemental Cash Flow Information [Abstract]
Interest Paid, Excluding Capitalized Interest, Operating Activity	219,035	241,667
Servicing Asset at Fair Value, Additions	2,246		$ 8,716
Board Authorized Purchase Program [Member]
Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract]
Payments for Repurchase of Common Stock	(25,202)	(22,292)
Performance/Service Based RSAs, RSA,
Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract]
Payments for Repurchase of Common Stock	(6,377)	(5,816)
Retained Earnings [Member]
Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract]
Net Income (Loss)	$ 119,635	$ 101,687