Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Defined Benefits Plan Estimated Future Employer Contributions In Next Fiscal Year			$ 2,300
Post-Retirement Health Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefits Plan Estimated Future Employer Contributions In Next Fiscal Year			$ 240
Service cost	$ 11	$ 10
Interest cost	26	31
Expected return on plan assets	0	0
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0	0
Net amortization of net (gain) loss	0	0
Net Periodic Benefit Cost	37	41
Defined Benefit Plan, Plan Assets, Contributions by Employer	56
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	339	325
Interest cost	658	779
Expected return on plan assets	(1,178)	(1,050)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0	0
Net amortization of net (gain) loss	518	492
Net Periodic Benefit Cost	337	$ 546
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 0