Retirement Plans, Pension and Postretirement Plans Table (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Fair Value Of Plan Assets As A Percentage Of Net Benefit Obligation	215.00%	196.00%
Change in Benefit Obligation
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	$ 0	$ 0	$ 1,494
RAP
Change in Fair Value of Plan Assets
Fair value of plan assets at beginning of year	407,405	497,796
Actual return on plan assets	60,565	(74,140)
Employer contributions	0	0
Gross benefits paid	(14,513)	(16,252)
Fair value of plan assets at end of year(a)	453,457	407,405	497,796
Change in Benefit Obligation
Net benefit obligation at beginning of year	208,315	261,321
Service cost	3,189	3,670	7,779
Interest cost	10,887	7,152	6,570
Actuarial (gain) loss	3,475	(47,577)
Gross benefits paid	(14,513)	(16,252)
Net benefit obligation at end of year(a)	211,353	208,315	261,321
Funded (unfunded) status	242,104	199,089
Noncurrent assets	242,104	199,089
Current liabilities	0	0
Noncurrent liabilities	0	0
Asset (liability) recognized on the consolidated balance sheets	$ 242,104	199,089
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.
Postretirement Plan
Change in Fair Value of Plan Assets
Fair value of plan assets at beginning of year	$ 0	0
Actual return on plan assets	0	0
Employer contributions	171	193
Gross benefits paid	(171)	(193)
Fair value of plan assets at end of year(a)	0	0	0
Change in Benefit Obligation
Net benefit obligation at beginning of year	1,530	1,975
Service cost	0	0
Interest cost	78	53	52
Actuarial (gain) loss	(12)	(305)
Gross benefits paid	(171)	(193)
Net benefit obligation at end of year(a)	1,425	1,530	$ 1,975
Funded (unfunded) status	(1,425)	(1,530)
Noncurrent assets	0	0
Current liabilities	(158)	(164)
Noncurrent liabilities	(1,267)	(1,366)
Asset (liability) recognized on the consolidated balance sheets	$ (1,425)	$ (1,530)
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.