Long-Term Debt (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument
Medium-term notes, maximum remaining maturity	12 years
Long-term debt	$ 25,312,000,000	$ 25,077,000,000	$ 21,631,000,000
Long-term debt outstanding maturity:
2014	6,592,000,000
2015	6,446,000,000
2016	4,796,000,000
2017	2,747,000,000
2018	2,350,000,000
Thereafter	2,381,000,000
Total	25,312,000,000	25,077,000,000	21,631,000,000
Medium-term notes
Debt Instrument
Long-term debt issued	6,150,000,000
Long-term debt issued at fixed interest rates	3,990,000,000
Long-term debt issued at floating interest rates	2,160,000,000
Long term debt, gross	23,837,000,000	23,488,000,000	20,058,000,000
Unamortized discount	(8,000,000)	(13,000,000)	(10,000,000)
Long-term debt	23,829,000,000	23,475,000,000	20,048,000,000
Long-term debt, Avg. Rate	2.80%	3.20%	3.90%
Long-term debt outstanding maturity:
Total	23,829,000,000	23,475,000,000	20,048,000,000
Bank borrowings
Debt Instrument
Long-term debt	1,483,000,000	1,602,000,000	1,583,000,000
Long-term debt, Avg. Rate	3.20%	4.10%	3.70%
Long-term debt outstanding maturity:
Total	$ 1,483,000,000	$ 1,602,000,000	$ 1,583,000,000