Debt (Details) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Average Contractual (interest rate)	3.40%	3.70%
Average Effective (interest rate)	3.70%	4.00%
Total short-term debt	$ 14,075,000,000	$ 16,024,000,000
Unamortized discount	(138,000,000)	(149,000,000)
Fair value adjustments	867,000,000	681,000,000
Total long-term debt	70,639,000,000	68,635,000,000
Total debt	84,714,000,000	84,659,000,000
Fair value of debt	88,187,000,000	86,785,000,000
Fair value of short-term debt	7,500,000,000	6,400,000,000
Asset-backed commercial paper [Member]
Debt Instrument [Line Items]
Average Contractual (interest rate)	0.40%	0.30%
Total short-term debt	5,824,000,000	6,835,000,000
Floating Rate Demand Notes [Member]
Debt Instrument [Line Items]
Average Contractual (interest rate)	1.10%	1.30%
Total short-term debt	4,962,000,000	4,713,000,000
Other asset-backed short-term debt [Member]
Debt Instrument [Line Items]
Average Contractual (interest rate)	1.30%	1.50%
Total short-term debt	766,000,000	2,741,000,000
Unsecured commercial paper [Member]
Debt Instrument [Line Items]
Average Contractual (interest rate)	1.60%	5.40%
Total short-term debt	1,176,000,000	156,000,000
Other short-term debt [Member]
Debt Instrument [Line Items]
Average Contractual (interest rate)	6.00%	7.00%
Total short-term debt	1,347,000,000	1,579,000,000
Total short-term debt [Member]
Debt Instrument [Line Items]
Average Contractual (interest rate)	1.30%	1.40%
Average Effective (interest rate)	1.30%	1.40%
Senior indebtedness [Member]
Debt Instrument [Line Items]
Notes payable within one year	3,078,000,000	6,127,000,000
Notes payable after one year	32,381,000,000	24,892,000,000
Asset-backed debt [Member]
Debt Instrument [Line Items]
Notes payable within one year	14,815,000,000	16,526,000,000
Notes payable after one year	$ 19,636,000,000	$ 20,558,000,000
Total long-term debt [Member]
Debt Instrument [Line Items]
Average Contractual (interest rate)	3.80%	4.20%
Average Effective (interest rate)	4.20%	4.60%