Long-Term Debt and Short-Term Borrowings - Long-Term Debt Issuances (Details) $ in Millions	1 Months Ended
	Feb. 28, 2019 USD ($)
Fixed rate medium term note due 2022
Debt instrument
Principal amount	$ 450
Term of debt instrument	3 years
Interest rate - effective	2.75%
Fixed rate medium term notes due 2024
Debt instrument
Principal amount	$ 500
Term of debt instrument	5 years
Interest rate - effective	3.25%
Fixed rate medium term notes due 2029
Debt instrument
Principal amount	$ 800
Term of debt instrument	10 years
Interest rate - effective	3.375%
Fixed rate medium term note due 2048
Debt instrument
Principal amount	$ 500
Term of debt instrument	29 years 6 months
Interest rate - effective	4.00%