Pension Plans and Postretirement Benefit Plan - Schedule of Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Pension Benefits
Net periodic benefit cost for pension plans and the postretirement benefit plan
Service Cost	$ 0	$ 0
Interest Cost	727	900
Expected Return on Plan Assets	(1,148)	(1,258)
Amortization of Prior Service Credit	0	0
Amortization of Net Actuarial Losses	662	570
Net Periodic Benefit Cost	241	212
Postretirement Benefits
Net periodic benefit cost for pension plans and the postretirement benefit plan
Service Cost	176	151
Interest Cost	206	231
Expected Return on Plan Assets	0	0
Amortization of Prior Service Credit	(61)	(61)
Amortization of Net Actuarial Losses	0	0
Net Periodic Benefit Cost	$ 321	$ 321