Short-term Borrowings and Other Debt Obligations Line of Credit (Details) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Line of Credit Facility [Line Items]
Debt and Lease Obligation	$ 2,161		$ 7,662
A&R Credit Agreement [Member]
Line of Credit Facility [Line Items]
Short-term Debt		$ 0	0
Committed Letters of Credit [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	$ 399
Term Loan Borrowings before Debt Issuance Cost [Member]
Line of Credit Facility [Line Items]
Debt and Lease Obligation			310
A&R Credit Agreement [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			529
A&R Credit Agreement [Member] | Extending Lenders [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 303