Debt (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Debt Instrument [Line Items]
Gains (Losses) on Extinguishment of Debt	$ 1,000,000	$ 6,000,000	$ 1,000,000	$ 9,000,000
Average Contractual (interest rate)	3.00%		3.00%		3.30%
Average Effective (interest rate)	3.20%		3.20%		3.50%
Unamortized discount	(109,000,000)		(109,000,000)		(128,000,000)
Fair value adjustments	210,000,000		210,000,000		791,000,000
Total debt	90,822,000,000		90,822,000,000		89,258,000,000
Accrued interest included in fair value of debt	596,000,000		596,000,000		708,000,000
Fair value of debt	93,425,000,000		93,425,000,000		92,799,000,000
Fair value of short-term debt	8,000,000,000		8,000,000,000		8,000,000,000
Unsecured Debt [Member]
Debt Instrument [Line Items]
Gains (Losses) on Extinguishment of Debt	1,000,000		1,000,000
Total debt	48,055,000,000		48,055,000,000
Asset-backed commercial paper [Member]
Debt Instrument [Line Items]
Average Contractual (interest rate)	0.30%		0.30%		0.40%
Total short-term debt	4,813,000,000		4,813,000,000		5,752,000,000
Floating Rate Demand Notes [Member]
Debt Instrument [Line Items]
Average Contractual (interest rate)	1.10%		1.10%		1.10%
Total short-term debt	5,183,000,000		5,183,000,000		4,890,000,000
Other asset-backed short-term debt [Member]
Debt Instrument [Line Items]
Average Contractual (interest rate)	1.00%		1.00%		1.10%
Total short-term debt	733,000,000		733,000,000		3,616,000,000
Unsecured commercial paper [Member]
Debt Instrument [Line Items]
Average Contractual (interest rate)	1.20%		1.20%		1.20%
Total short-term debt	1,535,000,000		1,535,000,000		1,686,000,000
Other short-term debt [Member]
Debt Instrument [Line Items]
Average Contractual (interest rate)	4.80%		4.80%		4.70%
Total short-term debt	1,237,000,000		1,237,000,000		1,434,000,000
Total short-term debt [Member]
Debt Instrument [Line Items]
Average Contractual (interest rate)	1.20%		1.20%		1.10%
Average Effective (interest rate)	1.20%		1.20%		1.10%
Total short-term debt	13,501,000,000		13,501,000,000		17,378,000,000
Senior indebtedness [Member]
Debt Instrument [Line Items]
Notes payable within one year	5,967,000,000		5,967,000,000		5,557,000,000
Notes payable after one year	34,133,000,000		34,133,000,000		31,656,000,000
Asset-backed debt [Member]
Debt Instrument [Line Items]
Notes payable within one year	16,544,000,000		16,544,000,000		13,788,000,000
Notes payable after one year	20,576,000,000		20,576,000,000		20,216,000,000
Total long-term debt [Member]
Debt Instrument [Line Items]
Average Contractual (interest rate)	3.40%		3.40%		3.80%
Average Effective (interest rate)	3.50%		3.50%		4.10%
Total long-term debt	$ 77,321,000,000		$ 77,321,000,000		$ 71,880,000,000