Retirement Plans, Pension and Postretirement Plans Table (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Change in Benefit Obligation
Fair Value Of Plan Assets As A Percentage Of Net Benefit Obligation	224.00%	215.00%
RAP
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Description	The Corporation has a noncontributory defined benefit RAP, covering substantially all employees who meet participation requirements. The benefits are based primarily on years of service and the employee’s compensation paid. Employees of acquired entities generally participate in the RAP after consummation of the business combinations. Any retirement plans of acquired entities are typically merged into the RAP after completion of the mergers, and credit is usually given to employees for years of service at the acquired institution for vesting and eligibility purposes.
Change in Fair Value of Plan Assets
Defined Benefit Plan, Plan Assets, Amount, Beginning Balance	$ 453,457	$ 407,405
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	43,676	60,565
Defined Benefit Plan, Plan Assets, Contributions by Employer	0	0
Defined Benefit Plan, Plan Assets, Benefits Paid	(18,163)	(14,513)
Defined Benefit Plan, Plan Assets, Amount, Ending Balance	478,970	453,457	$ 407,405
Change in Benefit Obligation
Defined Benefit Plan, Benefit Obligation, Beginning Balance	211,353	208,315
Defined Benefit Plan, Service Cost	3,027	3,189	3,670
Defined Benefit Plan, Interest Cost	11,173	10,887	7,152
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	5,975	3,475
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(18,163)	(14,513)
Defined Benefit Plan, Benefit Obligation, Ending Balance	213,365	211,353	208,315
Defined Benefit Plan, Funded (Unfunded) Status of Plan	265,605	242,104
Assets for Plan Benefits, Defined Benefit Plan	265,605	242,104
Liability, Defined Benefit Plan, Current	0	0
Liability, Defined Benefit Plan, Noncurrent	0	0
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position, Total	$ 265,605	242,104
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Description	The Corporation also provides legacy healthcare access to a limited group of retired employees from a previous acquisition in the Postretirement Plan. There are no other active retiree healthcare plans.
Change in Fair Value of Plan Assets
Defined Benefit Plan, Plan Assets, Amount, Beginning Balance	$ 0	0
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	0	0
Defined Benefit Plan, Plan Assets, Contributions by Employer	183	171
Defined Benefit Plan, Plan Assets, Benefits Paid	(183)	(171)
Defined Benefit Plan, Plan Assets, Amount, Ending Balance	0	0	0
Change in Benefit Obligation
Defined Benefit Plan, Benefit Obligation, Beginning Balance	1,425	1,530
Defined Benefit Plan, Service Cost	0	0
Defined Benefit Plan, Interest Cost	73	78	53
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	729	(12)
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(183)	(171)
Defined Benefit Plan, Benefit Obligation, Ending Balance	2,043	1,425	$ 1,530
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(2,043)	(1,425)
Assets for Plan Benefits, Defined Benefit Plan	0	0
Liability, Defined Benefit Plan, Current	(212)	(158)
Liability, Defined Benefit Plan, Noncurrent	(1,832)	(1,267)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position, Total	$ (2,043)	$ (1,425)