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Mortgage Banking Activities, Mortgage Servicing Rights (Details) | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2025 USD ($) | Sep. 30, 2024 USD ($) | Sep. 30, 2025 USD ($) | Sep. 30, 2024 USD ($) | Dec. 31, 2024 USD ($)
Summary of Mortgage Servicing Rights [Abstract] |  |  |  |  |
Number of residential mortgage loans serviced for others | 124,909 |  | 124,909 |  | 125,728
Outstanding principal balance of residential mortgage loans serviced for others | $ 22,145,687,000 |  | $ 22,145,687,000 |  | $ 22,269,513,000
Weighted average interest rate | 3.82% |  | 3.82% |  | 3.73%
Remaining term (in months) |  |  | 272 months |  | 276 months
Servicing Asset at Fair Value, Amount [Roll Forward] |  |  |  |  |
Beginning balance | $ 334,644,000 | $ 333,246,000 | $ 338,145,000 | $ 293,884,000 | $ 293,884,000
Additions | 3,403,000 | 3,842,000 | 8,975,000 | 10,812,000 |
Acquisitions | 0 | 3,334,000 | 14,615,000 | 34,755,000 |
Changes due to principal payments | (9,273,000) | (8,049,000) | (20,702,000) | (21,508,000) |
Change in fair value due to market assumption changes | (2,375,000) | (16,453,000) | (14,634,000) | (2,023,000) |
Ending balance | $ 326,399,000 | $ 315,920,000 | $ 326,399,000 | $ 315,920,000 | $ 338,145,000
Servicing Assets at Fair Value, Assumptions Used to Estimate Fair Value [Abstract] |  |  |  |  |
Discount rate - risk-free rate plus a market premium (in hundredths) |  |  | 9.21% |  | 9.60%
Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Prepayment Speed |  |  | 7.10% |  | 7.09%
Loan servicing costs - annually per loan based upon loan type, performing, minimum (in dollars per loan) |  |  | $ 73 |  | $ 73
Loan servicing costs - annually per loan based upon loan type, performing, maximum (in dollars per loan) |  |  | 94 |  | 94
Loan servicing costs - annually per loan based upon loan type, delinquent, minimum (in dollars per loan) |  |  | 150 |  | 150
Loan servicing costs - annually per loan based upon loan type, delinquent, maximum (in dollars per loan) |  |  | 500 |  | 500
Loan servicing costs - annually per loan based upon loan type, foreclosure, minimum (in dollars per loan) |  |  | 875 |  | 875
Loan servicing costs - annually per loan based upon loan type, foreclosure, maximum (in dollars per loan) |  |  | $ 6,000 |  | $ 6,000
Escrow earnings rate - indexed to rates paid on deposit accounts with comparable average life (in hundredths) |  |  | 3.58% |  | 4.44%
Primary secondary mortgage rate spread | 128 |  | 128 |  | 115
Delinquency rate |  |  | 2.24% |  | 2.19%

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- Definition The escrow earning rate used to estimate the fair value of servicing assets, based on rates paid on deposit accounts. + References No definition available. + Details
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- Definition Amount of increase (decrease) in fair value from changes in the assumptions or model used to calculate the fair value of a contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer. + References No definition available. + Details
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- Definition Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 11 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-11 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 11 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-11 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-10 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 860 -SubTopic 50 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481229/860-50-50-3 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 860 -SubTopic 50 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481260/860-50-45-2 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 860 -SubTopic 50 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481260/860-50-45-1 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 860 -SubTopic 50 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481260/860-50-45-2 + Details
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