Allowance for Credit Losses and Recorded Investment in Finance Receivables by Portfolio Segment (Details) (USD $) In Millions, unless otherwise specified											3 Months Ended		6 Months Ended			3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Sep. 30, 2012 Retail Loan [Member]	Sep. 30, 2011 Retail Loan [Member]	Sep. 30, 2012 Commercial [Member]	Sep. 30, 2011 Commercial [Member]	Sep. 30, 2012 Finance Receivables, Net [Member]	Sep. 30, 2011 Finance Receivables, Net [Member]	Sep. 30, 2012 Finance Receivables, Net [Member]	Sep. 30, 2011 Finance Receivables, Net [Member]	Mar. 31, 2012 Finance Receivables, Net [Member]	Sep. 30, 2012 Finance Receivables, Net [Member] Retail Loan [Member]	Sep. 30, 2011 Finance Receivables, Net [Member] Retail Loan [Member]	Sep. 30, 2012 Finance Receivables, Net [Member] Retail Loan [Member]	Sep. 30, 2011 Finance Receivables, Net [Member] Retail Loan [Member]	Sep. 30, 2012 Finance Receivables, Net [Member] Commercial [Member]	Sep. 30, 2011 Finance Receivables, Net [Member] Commercial [Member]	Sep. 30, 2012 Finance Receivables, Net [Member] Commercial [Member]	Sep. 30, 2011 Finance Receivables, Net [Member] Commercial [Member]	Sep. 30, 2012 Finance Receivables, Net [Member] Dealer Products [Member]	Sep. 30, 2011 Finance Receivables, Net [Member] Dealer Products [Member]	Sep. 30, 2012 Finance Receivables, Net [Member] Dealer Products [Member]	Sep. 30, 2011 Finance Receivables, Net [Member] Dealer Products [Member]	Sep. 30, 2012 Investments In Operating Leases, Net [Member]	Mar. 31, 2012 Investments In Operating Leases, Net [Member]
Allowance for Credit Losses for Finance Receivables:
Allowance for credit losses at	$ 549	$ 606	$ 619	$ 623	$ 667	$ 879					$ 515	$ 528	$ 524	$ 754		$ 356	$ 380	$ 395	$ 595	$ 6	$ 13	$ 10	$ 18	$ 153	$ 135	$ 119	$ 141	$ 89	$ 95
Charge-offs											(65)	(68)	(110)	(121)		(65)	(67)	(109)	(120)	0	(1)	(1)	(1)	0	0	0	0
Recoveries											15	20	33	65		15	19	33	63	0	1	0	2	0	0	0	0
Provisions											(5)	30	13	(188)		27	43	14	(163)	(1)	(2)	(4)	(8)	(31)	(11)	3	(17)
Allowance for credit losses at	549	606	619	623	667	879					460	510	460	510		333	375	333	375	5	11	5	11	122	124	122	124	89	95
Ending Balance: Individually Evaluated for Impairment											45	52	45	52		0	0	0	0	0	0	0	0	45	52	45	52
Ending Balance: Collectively Evaluated for Impairment											415	458	415	458		333	375	333	375	5	11	5	11	77	72	77	72
Gross Finance Receivables:
Ending Balance at	61,672		58,611								61,672	56,203	61,672	56,203	58,611	47,355	45,925	47,355	45,925	361	389	361	389	13,956	9,889	13,956	9,889
Ending Balance: Individually Evaluated for Impairment											258	187	258	187		0	0	0	0	0	0	0	0	258	187	258	187
Ending Balance: Collectively Evaluated for Impairment											61,414	56,016	61,414	56,016		47,355	45,925	47,355	45,925	361	389	361	389	13,698	9,702	13,698	9,702
Gross Finance Receivables							$ 471	$ 573	$ 1	$ 1