Retirement Plans - Summary of Reconciliation of Level 3 Partnership Assets Within Fair Value Hierarchy (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of Level 3 fund assets
Beginning Balance	$ 282,696
Ending Balance	287,270	$ 282,696
Partnership
Reconciliation of Level 3 fund assets
Beginning Balance	7,539
Ending Balance	6,792	7,539
Significant Unobservable Inputs (Level 3)
Reconciliation of Level 3 fund assets
Beginning Balance	7,539
Ending Balance	6,792	7,539
Significant Unobservable Inputs (Level 3) | Partnership
Reconciliation of Level 3 fund assets
Beginning Balance	7,539	9,172
Capital contributions	44	120
Realized and unrealized gain	(269)	(139)
Capital distributions	(522)	(1,614)
Ending Balance	$ 6,792	$ 7,539