Retirement Benefits and Trusteed Assets (Pension Plan - Target Allocations of Plan Assets) (Details) - Pension plan	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage of assets	100.00%
U.S. Large Capitalization (Cap) Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage of assets	18.00%
U.S. Small Cap and Mid Cap Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage of assets	3.00%
Non-U.S. Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage of assets	16.00%
Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage of assets	38.00%
Hedge Funds and Similar Investments
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage of assets	14.00%
Private Equity and Other
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage of assets	11.00%