Retirement Plans, Pension and Postretirement Plans Table (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Fair Value Of Plan Assets As A Percentage Of Net Benefit Obligation	196.00%	190.00%
Change in Benefit Obligation
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	$ 0	$ 1,494	$ 0
RAP
Change in Fair Value of Plan Assets
Fair value of plan assets at beginning of year	497,796	478,849
Actual return on plan assets	(74,140)	41,576
Employer contributions	0	0
Gross benefits paid	(16,252)	(22,629)
Fair value of plan assets at end of year(a)	407,405	497,796	478,849
Change in Benefit Obligation
Net benefit obligation at beginning of year	261,321	280,017
Service cost	3,670	7,779	8,244
Interest cost	7,152	6,570	8,185
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	0	(1,494)
Actuarial (gain) loss	(47,577)	(8,921)
Gross benefits paid	(16,252)	(22,629)
Net benefit obligation at end of year(a)	208,315	261,321	280,017
Funded (unfunded) status	199,089	236,475
Noncurrent assets	199,089	236,475
Current liabilities	0	0
Noncurrent liabilities	0	0
Asset (liability) recognized on the consolidated balance sheets	$ 199,089	236,475
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	193	201
Gross benefits paid	(193)	(201)
Fair value of plan assets at end of year(a)	0	0	0
Change in Benefit Obligation
Net benefit obligation at beginning of year	1,975	2,243
Service cost	0	0
Interest cost	53	52	78
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	0	0
Actuarial (gain) loss	(305)	(119)
Gross benefits paid	(193)	(201)
Net benefit obligation at end of year(a)	1,530	1,975	$ 2,243
Funded (unfunded) status	(1,530)	(1,975)
Noncurrent assets	0	0
Current liabilities	(164)	(177)
Noncurrent liabilities	(1,366)	(1,798)
Asset (liability) recognized on the consolidated balance sheets	$ (1,530)	$ (1,975)
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.