Qualified Employee Benefit Plans - The Retirement Plan's Projected Benefit Obligation, Fair Value of Plan Assets and Funded Status (Details) - Retirement Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 100,480	$ 141,862
Interest cost	5,199	3,958	$ 3,794
Plan settlements	0	(4,524)
Actuarial (gain)	(984)	(37,839)
Benefits paid	(6,269)	(2,977)
Projected benefit obligation at end of year	98,426	100,480	141,862
Change in plan assets:
Plan assets at fair value at beginning of year	95,990	130,939
Actual return on plan assets	11,655	(27,448)
Plan settlements	0	(4,524)
Benefits paid	(6,269)	(2,977)
Plan assets at fair value at end of year	101,376	95,990	$ 130,939
Funded status	$ 2,950	$ (4,490)