Benefit Plans - Changes in obligations and plan assets (Details) - Modified Retirement Plan - Unfunded plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accumulated benefit obligation:
Accumulated benefit obligation - beginning of year	$ 27,099	$ 25,105
Service cost	659	588	$ 392
Interest cost	676	795	931
Actuarial (gains) losses	(1,066)	1,804
Benefits paid	(1,107)	(1,193)
Accumulated benefit obligation - end of year	26,261	27,099	25,105
Change in plan assets, at fair value:
Beginning plan assets	0	0
Employer contribution	1,107	1,193
Benefits paid	(1,107)	(1,193)
Plan assets - end of year	0	0	$ 0
Funded status - end of year (plan assets less benefit obligations)	$ (26,261)	$ (27,099)