Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended					9 Months Ended		12 Months Ended
	Sep. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Income (Loss)	$ 88,018	$ 81,169		$ 83,248	$ 103,360	$ 284,760	$ 273,762
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Provision for Loan, Lease, and Other Losses	20,991			21,943		68,000	62,014
Depreciation						36,414	34,703
Mortgage Servicing Rights (MSR) Impairment (Recovery)						959	(14,658)
Amortization of Intangible Assets	2,203			2,203		6,608	6,608
Accretion (Amortization) of Discounts and Premiums, Investments						30,998	27,394
Other Depreciation and Amortization						26,307	25,830
Marketable Securities, Gain (Loss)						(3,857)	0
Gain (Loss) on Disposition of Assets	474			(625)		1,407	(590)
Gain (Loss) on Sale of Mortgage Loans						2,284	2,154
Payment for Origination and Purchase, Loan, Held-for-Sale						(450,532)	(283,469)
Proceeds from Sale, Loan, Mortgage, Held-for-Sale						415,840	254,619
Increase (Decrease) in Other Operating Assets and Liabilities, Net [Abstract]
Increase (Decrease) in Accrued Interest Receivable, Net						1,792	(26,670)
Increase (Decrease) in Interest Payable, Net						19,507	69,461
Increase (Decrease) in Other Accounts Payable and Accrued Liabilities						332	(22,632)
Increase (Decrease) in Derivative Assets and Liabilities						(61,615)	3,721
Increase (Decrease) in Other Operating Assets and Liabilities, Net						(6,084)	(34,137)
Net Cash Provided by (Used in) Operating Activities, Total						373,120	378,110
Net Cash Provided by (Used in) Investing Activities [Abstract]
Payments for (Proceeds from) Loans and Leases						(795,057)	(1,436,901)
Payments for Investing Activities [Abstract]
Payments to Acquire Debt Securities, Available-for-Sale						(1,177,627)	(1,109,501)
Payments to Acquire Held-to-Maturity Securities						0	(41,524)
Payments to Acquire Federal Home Loan Bank Stock						(122,205)	(114,985)
Proceeds from Investing Activities [Abstract]
Proceeds from Sale of Debt Securities, Available-for-Sale						9,472	0
Proceeds from Sale of Federal Home Loan Bank Stock						196,049	131,272
Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-Sale						660,732	288,313
Proceeds from Maturities, Prepayments and Calls of Held-to-Maturity Securities						92,402	101,847
Proceeds from Sale and Maturity of Other Investments						12,759	20,224
Payments for (Proceeds from) Productive Assets						(31,702)	(43,541)
Net Change in Tax Credit Investments						(17,856)	(19,615)
Net Cash Provided by (Used in) Investing Activities, Total						(1,173,035)	(2,224,411)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Increase (Decrease) in Deposits						108,249	2,487,225
Proceeds from (Repayments of) Short-Term Debt						590,248	(154,292)
Increase (Decrease) in Loans from Federal Home Loan Banks						(35,000)	(580,000)
Payments of FHLBank Borrowings, Financing Activities						(727)	(568)
Proceeds from FHLBank Borrowings, Financing Activities						2,656	1,369
Proceeds from Issuance of Long-Term Debt						298,800	292,740
Payments of Debt Issuance Costs						(751)	0
Finance Lease, Principal Payments						(66)	(64)
Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Including Option Exercised						13,281	2,362
Payments of Ordinary Dividends, Common Stock						(100,633)	(96,005)
Payments of Ordinary Dividends, Preferred Stock and Preference Stock						(8,625)	(8,625)
Net Cash Provided by (Used in) Financing Activities, Total						843,134	1,937,635
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect, Total						43,219	91,334
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Beginning Balance		923,823	$ 712,789		621,455	923,823	621,455	$ 621,455
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Ending Balance	967,042		$ 923,823	712,789		967,042	712,789	923,823
Supplemental Cash Flow Information [Abstract]
Interest Paid, Excluding Capitalized Interest, Operating Activities						796,621	576,221
Income Taxes Paid, Net						6,963	68,382
Real Estate Owned, Transfer to Real Estate Owned						12,586	5,917
Servicing Asset at Fair Value, Additions						4,458	2,477	$ 3,564
Loan and Lease, Transfer from Held-in-Portfolio to Held-for-Sale						(74,737)	6,833
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	37,718			(6,762)		18,871	(19,391)
Board Authorized Purchase Program [Member]
Net Cash Provided by (Used in) Financing Activities [Abstract]
Payments for Repurchase of Common Stock						(18,289)	0
Other Assets [Member]
Supplemental Cash Flow Information [Abstract]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge						1,899	3,308
Other Liabilities [Member]
Supplemental Cash Flow Information [Abstract]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge						(10,369)	18,652
Performance/Service Based RSAs, RSA,
Net Cash Provided by (Used in) Financing Activities [Abstract]
Payments for Repurchase of Common Stock						(6,007)	(6,507)
Retained Earnings [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Income (Loss)	$ 88,018	$ 81,169		$ 83,248	$ 103,360	$ 284,760	$ 273,762