Retirement Plans - Reconciliation of Level 3 Fixed Annuity Contracts Within Fair Value Hierarchy (Details 13) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Level 3 fund assets
Beginning Balance	$ 259,752
Benefits paid	(145)	$ (157)
Ending Balance	282,696	259,752
Significant Unobservable Inputs (Level 3)
Reconciliation of Level 3 fund assets
Beginning Balance	9,172
Ending Balance	$ 7,539	$ 9,172