Debt Credit Facilities (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Line of credit facility	$ 3,540	$ 2,477
$4 billion credit facility due November 16, 2023
Line of Credit Facility [Line Items]
Line of credit facility	0	0
Line of Credit Facility, Current Borrowing Capacity	4,000
5-year Due 2023 Senior Unsecured Revolving Credit Facilities [Member]
Line of Credit Facility [Line Items]
Line of credit facility	0
Line of Credit Facility, Remaining Borrowing Capacity	3,917
Letters of Credit Outstanding, Amount	83
Commercial paper notes(a)
Line of Credit Facility [Line Items]
Line of credit facility	$ 0	$ 37