Retirement Benefits Pension Plan Contributions (Details) $ in Millions	6 Months Ended
	Jun. 30, 2020 USD ($)
Unfunded Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	$ 350
Pension Plan | Funded Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer	282
Pension Plan | Unfunded Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer	176
Minimum | Pension Plan | Funded Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	500
Maximum | Pension Plan | Funded Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	$ 700