Debt (Short Term Debt Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Aug. 31, 2016	Dec. 31, 2015
Short-term Debt [Line Items]
Short-term debt	$ 7,790,000,000		$ 8,162,000,000
Accounts receivable facility | Accounts Receivable Securitization Facility
Short-term Debt [Line Items]
Short-term debt	568,000,000		$ 571,000,000
Average outstanding amount	$ 551,000,000
Interest rate during period	1.20%
Maximum month-end outstanding amount	$ 621,000,000
Line of credit facility, maximum borrowing capacity		$ 625,000,000
Extension period	364 days
Collateral amount	$ 655,000,000