Mortgage Banking Activities, Mortgage Servicing Rights (Details)	3 Months Ended	12 Months Ended
Mar. 31, 2026 USD ($)	Mar. 31, 2025 USD ($)	Dec. 31, 2025 USD ($)
Summary of Mortgage Servicing Rights [Abstract]
Number of residential mortgage loans serviced for others	123,658		123,263
Outstanding principal balance of residential mortgage loans serviced for others	$ 21,989,466,000		$ 21,760,414,000
Weighted average interest rate	3.85%		3.83%
Remaining term (in months)	269 months		270 months
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	$ 322,724,000	$ 338,145,000	$ 338,145,000
Additions	4,010,000	2,509,000
Acquisitions	8,645,000	14,615,000
Changes due to principal payments	(10,153,000)	(5,918,000)
Change in fair value due to market assumption changes	8,155,000	(7,240,000)
Ending balance	$ 333,381,000	$ 342,111,000	$ 322,724,000
Servicing Assets at Fair Value, Assumptions Used to Estimate Fair Value [Abstract]
Discount rate - risk-free rate plus a market premium (in hundredths)	9.42%		9.31%
Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Prepayment Speed	6.93%		7.07%
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)	3.82%		3.66%
Primary secondary mortgage rate spread	125		128
Delinquency rate	2.10%		2.28%

The decrease in fair value as a result of loan runoff.

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- Definition

Mortgage rate spread between the primary and secondary market.

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No definition available.

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- Definition

Indicates the number of mortgage loans being serviced.

+ References

No definition available.

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Dollar amount of principal outstanding on mortgage loans being serviced.

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Represents the weighted average remaining term of mortgage loans being serviced fro others.

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No definition available.

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The value of new servicing assets, subsequently measured at fair value, acquired during the current period through purchases of financial assets.

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No definition available.

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- Definition

Servicing Assets at Fair Value Assumptions Used to Estimate Fair Value Delinquent Loan Service Cost Minimum

+ References

No definition available.

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Servicing Assets At Fair Value Assumptions Used to Estimate Fair Value Delinquent

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No definition available.

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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.

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- Definition

Servicing Assets At Fair Value Assumptions Used to Estimate Fair Value Foreclosure Loan Service Cost Maximum

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No definition available.

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Servicing Assets at Fair Value Assumptions Used to Estimate Fair Value Foreclosure Loan Service Cost Minimum

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No definition available.

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- Definition

The maximum cost to service a performing loan for the period used as a variable in estimating fair value.

+ References

No definition available.

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- Definition

The minimum cost to service a performing loan for the period used as a variable in estimating fair value.

+ References

No definition available.

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- Definition

Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Delinquency Rate

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No definition available.

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- Definition

-- None. No documentation exists for this element. --

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- Definition

Represents the weighted average interest rate of loans servicedf for others as of the balance sheet date.

+ References

No definition available.

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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.

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No definition available.

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- Definition

The value of new servicing assets, subsequently measured at fair value, acquired or created during the current period through purchases or from transfers of financial assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
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-URI https://asc.fasb.org/1943274/2147481229/860-50-50-3

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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
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

Discount rate used to estimate the fair value of servicing assets and servicing liabilities.

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- Definition

Estimated rate of prepayments of principal on servicing assets and servicing liabilities.

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