Allowance for Credit Losses and Recorded Investment in Finance Receivables by Portfolio Segment (Details) (USD $) In Millions, unless otherwise specified											3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Mar. 31, 2011	Dec. 31, 2012 Retail Loan [Member]	Dec. 31, 2011 Retail Loan [Member]	Dec. 31, 2012 Commercial [Member]	Dec. 31, 2011 Commercial [Member]	Dec. 31, 2012 Finance Receivables, Net [Member]	Dec. 31, 2011 Finance Receivables, Net [Member]	Dec. 31, 2012 Finance Receivables, Net [Member]	Dec. 31, 2011 Finance Receivables, Net [Member]	Mar. 31, 2012 Finance Receivables, Net [Member]	Dec. 31, 2012 Finance Receivables, Net [Member] Retail Loan [Member]	Dec. 31, 2011 Finance Receivables, Net [Member] Retail Loan [Member]	Dec. 31, 2012 Finance Receivables, Net [Member] Retail Loan [Member]	Dec. 31, 2011 Finance Receivables, Net [Member] Retail Loan [Member]	Dec. 31, 2012 Finance Receivables, Net [Member] Commercial [Member]	Dec. 31, 2011 Finance Receivables, Net [Member] Commercial [Member]	Dec. 31, 2012 Finance Receivables, Net [Member] Commercial [Member]	Dec. 31, 2011 Finance Receivables, Net [Member] Commercial [Member]	Dec. 31, 2012 Finance Receivables, Net [Member] Dealer Products [Member]	Dec. 31, 2011 Finance Receivables, Net [Member] Dealer Products [Member]	Dec. 31, 2012 Finance Receivables, Net [Member] Dealer Products [Member]	Dec. 31, 2011 Finance Receivables, Net [Member] Dealer Products [Member]	Dec. 31, 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	$ 560	$ 549	$ 619	$ 620	$ 623	$ 879					$ 460	$ 510	$ 524	$ 754		$ 333	$ 375	$ 395	$ 595	$ 5	$ 11	$ 10	$ 18	$ 122	$ 124	$ 119	$ 141	$ 81	$ 95
Charge-offs											(79)	(69)	(189)	(190)		(79)	(68)	(188)	(188)	0	(1)	(1)	(2)	0	0	0	0
Recoveries											14	19	47	84		13	17	46	80	1	2	1	4	0	0	0	0
Provisions											84	48	97	(140)		89	53	103	(110)	(1)	(3)	(5)	(11)	(4)	(2)	(1)	(19)
Allowance for credit losses at	560	549	619	620	623	879					479	508	479	508		356	377	356	377	5	9	5	9	118	122	118	122	81	95
Ending Balance: Individually Evaluated for Impairment											43	48	43	48		0	0	0	0	0	0	0	0	43	48	43	48
Ending Balance: Collectively Evaluated for Impairment											436	460	436	460		356	377	356	377	5	9	5	9	75	74	75	74
Gross Finance Receivables:
Ending Balance at	63,179		58,611								63,179	57,805	63,179	57,805	58,611	47,880	45,651	47,880	45,651	362	376	362	376	14,937	11,778	14,937	11,778
Ending Balance: Individually Evaluated for Impairment											259	203	259	203		0	0	0	0	0	0	0	0	259	203	259	203
Ending Balance: Collectively Evaluated for Impairment											62,920	57,602	62,920	57,602		47,880	45,651	47,880	45,651	362	376	362	376	14,678	11,575	14,678	11,575
Gross Finance Receivables							$ 444	$ 537	$ 1	$ 1