Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Mar. 31, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract]
Net Income (Loss)	$ 124,732	$ 101,687	$ 88,018	$ 81,169	$ 337,648	$ 284,760
Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract]
Provision for Loan, Lease, and Other Losses	16,000		20,991		46,999	68,000
Depreciation					37,959	36,414
Mortgage Servicing Rights (MSR) Impairment (Recovery)					2,464	959
Amortization of Intangible Assets	2,203		2,203		6,608	6,608
Accretion (Amortization) of Discounts and Premiums, Investments					30,520	30,998
Other Depreciation and Amortization					26,307	26,307
Marketable Securities, Gain (Loss)					0	(3,857)
Gain (Loss) on Disposition of Assets	(3,340)		474		(727)	1,407
(Gain) loss on mortgage banking activities, net					103	2,284
Gain (Loss) on Sale of Mortgage Loans	0		0		6,976	0
Payment for Origination and Purchase, Loan, Held-for-Sale					(470,456)	(450,532)
Proceeds from Sale, Loan, Mortgage, Held-for-Sale					451,869	415,840
Increase (Decrease) in Other Operating Assets and Liabilities, Net [Abstract]
Increase (Decrease) in Accrued Interest Receivable, Net					(678)	1,792
Increase (Decrease) in Interest Payable, Net					(28,163)	19,507
Increase (Decrease) in Other Accounts Payable and Accrued Liabilities					(18,790)	332
Increase (Decrease) in Derivative Assets and Liabilities					(63,192)	(61,615)
Increase (Decrease) in Other Operating Assets and Liabilities, Net					32,162	(6,084)
Net Cash Provided by (Used in) Operating Activities, Total					397,610	373,120
Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract]
Payments for (Proceeds from) Loans and Leases					(1,224,724)	(795,057)
Payment for Investing Activity [Abstract]
Payments to Acquire Debt Securities, Available-for-Sale					(1,355,308)	(1,177,627)
Payments to Acquire Held-to-Maturity Securities					(994)	0
Payments to Acquire Federal Home Loan Bank Stock					(187,426)	(122,205)
Proceeds from Investing Activity [Abstract]
Proceeds from Sale of Debt Securities, Available-for-Sale					0	9,472
Proceeds from Sale of Federal Home Loan Bank Stock					112,964	196,049
Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-Sale					761,540	660,732
Proceeds from Maturities, Prepayments and Calls of Held-to-Maturity Securities					106,160	92,402
Proceeds from Sale and Maturity of Other Investments					18,929	12,759
Payments for (Proceeds from) Productive Assets					(28,591)	(31,702)
Net Change in Tax Credit Investments					(16,800)	(17,856)
Net Cash Provided by (Used in) Investing Activities, Total					(1,249,875)	(1,173,035)
Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract]
Increase (Decrease) in Deposits					233,419	108,249
Proceeds from (Repayments of) Short-Term Debt					(70,704)	590,248
Increase (Decrease) in Loans from Federal Home Loan Banks					1,560,000	(35,000)
Payments of FHLBank Borrowings, Financing Activities					(400,198)	(727)
Proceeds from FHLBank Borrowings, Financing Activities					200,898	2,656
Proceeds from Issuance of Long-Term Debt					0	298,800
Payments of Debt Issuance Costs					0	(751)
Finance Lease, Principal Payments					(67)	(66)
Repayments of Senior Debt					(250,000)	0
Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Including Option Exercised					4,876	13,281
Payments of Ordinary Dividends, Common Stock					(115,566)	(100,633)
Payments of Ordinary Dividends, Preferred Stock and Preference Stock					(8,625)	(8,625)
Proceeds from (Payment for) Other Financing Activity					(52)	0
Net Cash Provided by (Used in) Financing Activities, Total					1,125,433	843,134
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect, Total					273,168	43,219
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Beginning Balance		1,019,604		923,823	1,019,604	923,823	$ 923,823
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Ending Balance	1,292,772		967,042		1,292,772	967,042	1,019,604
Supplemental Cash Flow Information [Abstract]
Interest Paid, Excluding Capitalized Interest, Operating Activity					763,622	796,621
Income Taxes Paid, Net					(14,159)	6,963
Real Estate Owned, Transfer to Real Estate Owned					24,424	12,586
Servicing Asset at Fair Value, Additions					6,162	4,458	$ 6,707
Loan and Lease, Transfer from Held-in-Portfolio to Held-for-Sale					(54,339)	(74,737)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax (Deprecated 2025)					14,518	18,871
Proceeds from Sale of Mortgage Portfolio					564,375	0
Board Authorized Purchase Program [Member]
Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract]
Payments for Repurchase of Common Stock					(22,292)	(18,289)
Other Liabilities [Member]
Supplemental Cash Flow Information [Abstract]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge					(11,793)	(10,369)
Other Assets [Member]
Supplemental Cash Flow Information [Abstract]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge					(1,811)	1,899
Performance/Service Based RSAs, RSA,
Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract]
Payments for Repurchase of Common Stock					(6,256)	(6,007)
Retained Earnings [Member]
Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract]
Net Income (Loss)	$ 124,732	$ 101,687	$ 88,018	$ 81,169	$ 337,648	$ 284,760