Long-Term Debt and Short-Term Borrowings - Floating Rate Notes (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2004	Dec. 31, 2019
Floating rate notes due 2027 and 2040 and 2041
Number of years after date of issuance that put options commence		10 years
Floating rate note due 2044
Debt Instrument Term	40 years
Debt Instrument, Face Amount	$ 60	$ 55
Repurchase price of floating rate notes (as a percent)		100.00%
Maximum | Floating rate notes due 2027 and 2040 and 2041
Repurchase price of floating rate notes (as a percent)		100.00%
Minimum | Floating rate notes due 2027 and 2040 and 2041
Repurchase price of floating rate notes (as a percent)		99.00%