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, 2021	Dec. 31, 2020	Dec. 31, 2019
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 151,124,000	$ 136,113,000
Interest cost	3,794,000	4,443,000	$ 4,944,000
Plan settlements	(5,803,000)	0
Actuarial (gain) loss	(4,447,000)	16,131,000
Benefits paid	(2,806,000)	(5,563,000)
Projected benefit obligation at end of year	141,862,000	151,124,000	136,113,000
Change in plan assets:
Plan assets at fair value at beginning of year	125,022,000	114,080,000
Actual return on plan assets	14,526,000	16,505,000
Employer contribution	0	0
Plan settlements	(5,803,000)	0
Benefits paid	(2,806,000)	(5,563,000)
Plan assets at fair value at end of year	130,939,000	125,022,000	$ 114,080,000
Funded status	$ (10,923,000)	$ (26,102,000)