Allowance for Credit Losses and Recorded Investment in Finance Receivables by Portfolio Segment (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Mar. 31, 2013
Allowance for Credit Losses for Finance Receivables:
Allowance for credit losses at	$ 527	$ 619
Provision for credit losses	11	16
Allowance for credit losses at	501	606
Gross Finance Receivables:
Ending Balance at	64,519		63,172
Retail Loan [Member]
Gross Finance Receivables:
Gross Finance Receivables	389	476
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	445	524
Charge-offs	(50)	(45)
Recoveries	19	18
Provision for credit losses	10	18
Allowance for credit losses at	424	515
Ending Balance: Individually Evaluated for Impairment	35	75
Ending Balance: Collectively Evaluated for Impairment	389	440
Gross Finance Receivables:
Ending Balance at	64,519	60,475	63,172
Ending Balance: Individually Evaluated for Impairment	240	258
Ending Balance: Collectively Evaluated for Impairment	64,279	60,217
Finance Receivables, Net [Member] | Retail Loan [Member]
Allowance for Credit Losses for Finance Receivables:
Allowance for credit losses at	333	395
Charge-offs	(49)	(44)
Recoveries	19	18
Provision for credit losses	6	(13)
Allowance for credit losses at	309	356
Ending Balance: Individually Evaluated for Impairment	0	0
Ending Balance: Collectively Evaluated for Impairment	309	356
Gross Finance Receivables:
Ending Balance at	48,347	46,024
Ending Balance: Individually Evaluated for Impairment	0	0
Ending Balance: Collectively Evaluated for Impairment	48,347	46,024
Finance Receivables, Net [Member] | Commercial [Member]
Allowance for Credit Losses for Finance Receivables:
Allowance for credit losses at	5	10
Charge-offs	(1)	(1)
Recoveries	0	0
Provision for credit losses	(1)	(3)
Allowance for credit losses at	3	6
Ending Balance: Individually Evaluated for Impairment	0	0
Ending Balance: Collectively Evaluated for Impairment	3	6
Gross Finance Receivables:
Ending Balance at	379	360
Ending Balance: Individually Evaluated for Impairment	0	0
Ending Balance: Collectively Evaluated for Impairment	379	360
Finance Receivables, Net [Member] | Dealer Products [Member]
Allowance for Credit Losses for Finance Receivables:
Allowance for credit losses at	107	119
Charge-offs	0	0
Recoveries	0	0
Provision for credit losses	5	34
Allowance for credit losses at	112	153
Ending Balance: Individually Evaluated for Impairment	35	75
Ending Balance: Collectively Evaluated for Impairment	77	78
Gross Finance Receivables:
Ending Balance at	15,793	14,091
Ending Balance: Individually Evaluated for Impairment	240	258
Ending Balance: Collectively Evaluated for Impairment	15,553	13,833
Investments In Operating Leases, Net [Member]
Allowance for Credit Losses for Finance Receivables:
Allowance for credit losses at			82
Allowance for credit losses at	$ 77		$ 82