Long-term and Short-term Debt (Short-term with Maturities of Year or Less) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
Commercial paper	$ 100	$ 99
Other Short-term Borrowings	293	136
Short-term Debt	393	235
Average daily balance	$ 326	$ 216
Average days outstanding	69 days	34 days