Benefit Plans - Components of Company Plan Benefit Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Change in Projected Benefit Obligation
Projected benefit obligation, beginning of period			$ 33,530	$ 37,551	$ 37,551
Service cost	$ 351	$ 313	1,053	940	1,254
Interest cost	319	$ 326	956	979	1,306
Actuarial gain			0		3,180
Other reclassification			0		(8,925)
Benefits paid			(649)		(836)
Projected benefit obligation, end of period	34,890		34,890		33,530
Change in Plan Assets
Plan assets at fair value, beginning of period			0	$ 0	0
Company contributions			649		836
Benefits paid			(649)		(836)
Plan assets at fair value, end of period	0		0		0
Unfunded Status of the Plan	$ 34,890		$ 34,890		$ 33,530