Short-term Borrowings and Other Debt Obligations Schedule of Borrowing Availability (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Line of Credit Facility [Line Items]
Credit agreement, maximum capacity	$ 1,388
Short-term debt	253	$ 2
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Short-term debt	225	$ 0
Committed Letters of Credit [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	84
Term Loan Borrowings before Debt Issuance Cost [Member]
Line of Credit Facility [Line Items]
Debt and Capital Lease Obligations	$ 388