Employee Benefit Plans (Assumed Health Care Cost Trend Rates) (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Assumed annual increases in Medicare Part B trends after eight years	4.50%	4.50%
Minimum
Defined Benefit Plan Disclosure [Line Items]
Assumed annual increases in Medicare Part B trends for next eight years	2.87%	3.95%
Maximum
Defined Benefit Plan Disclosure [Line Items]
Assumed annual increases in Medicare Part B trends for next eight years	6.06%	8.02%