Allowance for Credit Losses and Recorded Investment in Finance Receivables by Portfolio Segment (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Allowance for Credit Losses for Finance Receivables:
Allowance for credit losses at	$ 619	$ 879	$ 1,705
Provision for credit losses	121	(98)	(433)
Allowance for credit losses at	527	619	879
Gross Finance Receivables:
Ending Balance at	63,172	58,611
Retail Loan [Member]
Gross Finance Receivables:
Gross Finance Receivables	415	502
Commercial [Member]
Gross Finance Receivables:
Gross Finance Receivables	1	1
Finance Receivables, Net [Member]
Allowance for Credit Losses for Finance Receivables:
Allowance for credit losses at	524	754
Charge-offs	(249)	(244)
Recoveries	71	103
Provision for credit losses	99	(89)
Allowance for credit losses at	445	524
Ending Balance: Individually Evaluated for Impairment	33	45
Ending Balance: Collectively Evaluated for Impairment	412	479
Gross Finance Receivables:
Ending Balance at	63,172	58,611
Ending Balance: Individually Evaluated for Impairment	241	211
Ending Balance: Collectively Evaluated for Impairment	62,931	58,400
Finance Receivables, Net [Member] | Retail Loan [Member]
Allowance for Credit Losses for Finance Receivables:
Allowance for credit losses at	395	595
Charge-offs	(248)	(243)
Recoveries	70	99
Provision for credit losses	116	(56)
Allowance for credit losses at	333	395
Ending Balance: Individually Evaluated for Impairment	0	0
Ending Balance: Collectively Evaluated for Impairment	333	395
Gross Finance Receivables:
Ending Balance at	47,808	45,383
Ending Balance: Individually Evaluated for Impairment	0	0
Ending Balance: Collectively Evaluated for Impairment	47,808	45,383
Finance Receivables, Net [Member] | Commercial [Member]
Allowance for Credit Losses for Finance Receivables:
Allowance for credit losses at	10	18
Charge-offs	(1)	(1)
Recoveries	1	4
Provision for credit losses	(5)	(11)
Allowance for credit losses at	5	10
Ending Balance: Individually Evaluated for Impairment	0	0
Ending Balance: Collectively Evaluated for Impairment	5	10
Gross Finance Receivables:
Ending Balance at	369	363
Ending Balance: Individually Evaluated for Impairment	0	0
Ending Balance: Collectively Evaluated for Impairment	369	363
Finance Receivables, Net [Member] | Dealer Products [Member]
Allowance for Credit Losses for Finance Receivables:
Allowance for credit losses at	119	141
Charge-offs	0	0
Recoveries	0	0
Provision for credit losses	(12)	(22)
Allowance for credit losses at	107	119
Ending Balance: Individually Evaluated for Impairment	33	45
Ending Balance: Collectively Evaluated for Impairment	74	74
Gross Finance Receivables:
Ending Balance at	14,995	12,865
Ending Balance: Individually Evaluated for Impairment	241	211
Ending Balance: Collectively Evaluated for Impairment	14,754	12,654
Investments In Operating Leases, Net [Member]
Allowance for Credit Losses for Finance Receivables:
Allowance for credit losses at	$ 82	$ 95