Employee Benefit Plans (Schedule of Benefits Plans) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pension Benefit Plan [Member]
Periodic costs for employee retirement benefit plans
Service Cost		$ 674	$ 609	$ 2,022	$ 1,826
Interest Cost		677	775	2,030	2,324
Expected Return on Assets		(1,556)	(1,409)	(4,669)	(4,226)
Amortization of Unrecognized Losses		717	515	2,151	1,544
Net Periodic Benefit Cost (Benefit)	[1]	512	490	1,534	1,468
Other Benefits Plan [Member]
Periodic costs for employee retirement benefit plans
Service Cost		229	248	687	745
Interest Cost		309	425	927	1,274
Expected Return on Assets		(786)	(721)	(2,357)	(2,163)
Amortization of Unrecognized Losses		132	338	396	1,014
Net Periodic Benefit Cost (Benefit)	[1]	$ (116)	$ 290	$ (347)	$ 870

[1] Service cost is included in Operations and Maintenance expense on the Condensed Consolidated Statements of Income; all other amounts are included in Other Income/Expense, net.