Long-term and Short-term Debt Long-term and Short-term Debt (Narrative - Line of Credit) (Details) - USD ($)	2 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2037	Dec. 01, 2037	Dec. 31, 2024	Dec. 31, 2023	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022	Nov. 01, 2017	Dec. 11, 2015
Committed Credit Facility Six [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date		Dec. 31, 2037
Line of Credit Facility, Remaining Borrowing Capacity		$ 436,000,000
Line of Credit Facility, Maximum Borrowing Capacity		2,896,000,000
Line of Credit Facility, Current Borrowing Capacity		$ 2,700,000,000
General Credit Facility Three [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date		Dec. 20, 2021
Line of Credit Facility, Remaining Borrowing Capacity		$ 2,254,000,000
Line of Credit Facility, Maximum Borrowing Capacity		$ 3,000,000,000.0
Committed Credit Facility Three [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date		Dec. 28, 2024
Line of Credit Facility, Remaining Borrowing Capacity		$ 4,000,000
Line of Credit Facility, Maximum Borrowing Capacity		400,000,000
Committed Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity		440,000,000
Line of Credit Facility, Maximum Borrowing Capacity		3,296,000,000
Other Notes MPEH [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 75,000,000
Amendment [Member] | Other Notes MPEH [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Maturity Date	Nov. 15, 2022	Nov. 20, 2024
Line of Credit Facility, Maximum Borrowing Capacity												$ 75,000,000	$ 100,000,000
Committed Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 3,300,000,000
Line of Credit Facility, Commitment Fee Amount		12,000,000	$ 15,000,000	$ 21,000,000
General Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Commitment Fee Amount		$ 12,000,000	$ 10,000,000	$ 13,000,000
Forecast [Member] | Committed Credit Facility Six [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					$ 0	$ 2,000,000,000.0
Forecast [Member] | Committed Credit Facility Three [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity							$ 0	$ 260,000,000	$ 310,000,000	$ 360,000,000	$ 380,000,000