Long-term and Short-term Debt Long-term and Short-term Debt (Narrative - Line of Credit) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2037	Dec. 01, 2037
Committed Credit Facility Six [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 404,000,000
Line of Credit Facility, Maximum Borrowing Capacity	2,896,000,000
Line of Credit Facility, Current Borrowing Capacity	2,800,000,000
General Credit Facility Three [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	2,541,000,000
Line of Credit Facility, Maximum Borrowing Capacity	3,000,000,000
Committed Credit Facility Three [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	0
Line of Credit Facility, Maximum Borrowing Capacity	350,000,000
Committed Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	404,000,000
Line of Credit Facility, Maximum Borrowing Capacity	3,246,000,000
Committed Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	3,200,000,000
Line of Credit Facility, Commitment Fee Amount	12,000,000	$ 12,000,000	$ 12,000,000
General Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Commitment Fee Amount	$ 10,000,000	$ 14,000,000	$ 12,000,000
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