Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 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	$ 9	$ 9	$ 19	$ 17
Interest cost	31	36	62	73
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	(8)
Net Periodic Benefit Cost	40	41	81	82
Defined Benefit Plan, Plan Assets, Contributions by Employer			119
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	325	304	650	609
Interest cost	779	866	1,558	1,733
Expected return on plan assets	(1,049)	(896)	(2,099)	(1,793)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0	0	0	0
Net amortization of net (gain) loss	492	390	984	779
Net Periodic Benefit Cost	$ 547	$ 664	1,093	$ 1,328
Defined Benefit Plan, Plan Assets, Contributions by Employer			$ 1,200