Qualified Employee Benefit Plans - The Retirement Plan's Projected Benefit Obligation, Fair Value of Plan Assets and Funded Status (Details) - Retirement Plan - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 141,862,000	$ 151,124,000
Interest cost	3,958,000	3,794,000	$ 4,443,000
Plan settlements	(4,524,000)	(5,803,000)
Actuarial (gain)	(37,839,000)	(4,447,000)
Benefits paid	(2,977,000)	(2,806,000)
Projected benefit obligation at end of year	100,480,000	141,862,000	151,124,000
Change in plan assets:
Plan assets at fair value at beginning of year	130,939,000	125,022,000
Actual return on plan assets	(27,448,000)	14,526,000
Employer contribution	0	0
Plan settlements	(4,524,000)	(5,803,000)
Benefits paid	(2,977,000)	(2,806,000)
Plan assets at fair value at end of year	95,990,000	130,939,000	$ 125,022,000
Funded status	$ (4,490,000)	$ (10,923,000)