Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Defined Benefits Plan Estimated Future Employer Contributions In Next Fiscal Year					$ 3,700
Post-Retirement Health Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefits Plan Estimated Future Employer Contributions In Next Fiscal Year					$ 251
Service cost	$ 10	$ 9	$ 29	$ 26
Interest cost	32	36	94	109
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	(4)	0	(12)
Net Periodic Benefit Cost	42	41	123	123
Defined Benefit Plan, Plan Assets, Contributions by Employer			176
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	325	304	975	913
Interest cost	779	866	2,337	2,599
Expected return on plan assets	(1,050)	(896)	(3,149)	(2,689)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	1	0	1	1
Net amortization of net (gain) loss	492	389	1,476	1,168
Net Periodic Benefit Cost	$ 547	$ 663	1,640	$ 1,992
Defined Benefit Plan, Plan Assets, Contributions by Employer			$ 3,000