Short-Term Borrowings (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Short-term Debt
Short-term borrowings, Balance	$ 4,699	$ 3,663	$ 4,651
Commercial paper, net
Short-term Debt
Short-term borrowings, Balance	3,688	2,502	3,654
Short-term borrowings, Avg. Rate	0.30%	0.50%	0.60%
Bank borrowings
Short-term Debt
Short-term borrowings, Balance	411	545	418
Short-term borrowings, Avg. Rate	6.80%	6.40%	5.60%
Variable denomination floating rate demand notes
Short-term Debt
Short-term borrowings, Balance	$ 600	$ 616	$ 579
Short-term borrowings, Avg. Rate	0.80%	0.80%	0.80%