Debt (Short Term Debt Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012	Nov. 30, 2009
Short-term Debt [Line Items]
Short-term debt	$ 8,052,000,000		$ 7,173,000,000
4 percent Convertible Senior Notes
Short-term Debt [Line Items]
Stated interest rate	4.00%		4.00%		4.00%
Subsidiaries
Short-term Debt [Line Items]
Short-term debt	8,020,000,000		7,037,000,000
Accounts receivable facility | Accounts Receivable Securitization Facility
Short-term Debt [Line Items]
Average outstanding amount	473,000,000
Interest rate during period	0.80%
Maximum month-end outstanding amount	550,000,000
Line of credit facility, maximum borrowing capacity	550,000,000
Extension period	364 days
Collateral amount	662,000,000
Accounts receivable facility | Subsidiaries | Accounts Receivable Securitization Facility
Short-term Debt [Line Items]
Short-term debt	548,000,000	[1]	430,000,000	[1]
Convertible debt | 4 percent Convertible Senior Notes
Short-term Debt [Line Items]
Short-term debt	$ 32,000,000		$ 136,000,000
Stated interest rate	4.00%		4.00%		4.00%	4.00%

[1] $946 and $2 were available under our ABL facility and accounts receivable securitization facility, respectively, at December 31, 2014. The ABL facility availability is reflected net of $50 of letters of credit. At December 31, 2014, the interest rates applicable to our ABL facility and accounts receivable securitization facility were 2.2 percent and 0.8 percent, respectively.