Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 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	$ 10	$ 10	$ 32	$ 29
Interest cost	26	32	77	94
Expected return on plan assets	0	0	0	0
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0	0	0	0
Net amortization of net (gain) loss	0	0	0	0
Net Periodic Benefit Cost	36	42	109	123
Defined Benefit Plan, Plan Assets, Contributions by Employer			167
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	339	325	1,016	975
Interest cost	658	779	1,974	2,337
Expected return on plan assets	(1,178)	(1,050)	(3,535)	(3,149)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0	1	0	1
Net amortization of net (gain) loss	518	492	1,554	1,476
Net Periodic Benefit Cost	$ 337	$ 547	1,009	$ 1,640
Defined Benefit Plan, Plan Assets, Contributions by Employer			$ 1,500