Allowance for Credit Losses (Past Dues) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Mar. 31, 2013
Past Due Finance Receivables and Investments in Operating Leases
Finance receivables	$ 144	$ 119
Operating leases	37	36
Total	181	155
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	499	460
60-89 Days Past Due	112	88
90 Days Past Due	32	31
Total Past Due	643	579
Current	63,876	62,593
Total Finance Receivables	64,519	63,172
Carrying Amount 90 Days Past Due and Accruing	32	31
Retail Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	492	454
60-89 Days Past Due	111	87
90 Days Past Due	32	31
Total Past Due	635	572
Current	47,712	47,236
Total Finance Receivables	48,347	47,808
Carrying Amount 90 Days Past Due and Accruing	32	31
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	6	6
60-89 Days Past Due	1	1
90 Days Past Due	0	0
Total Past Due	7	7
Current	372	362
Total Finance Receivables	379	369
Carrying Amount 90 Days Past Due and Accruing	0	0
Wholesale [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
90 Days Past Due	0	0
Total Past Due	0	0
Current	9,451	8,689
Total Finance Receivables	9,451	8,689	[1]
Carrying Amount 90 Days Past Due and Accruing	0	0
Real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1	0
60-89 Days Past Due	0	0
90 Days Past Due	0	0
Total Past Due	1	0
Current	4,583	4,580
Total Finance Receivables	4,584	4,580
Carrying Amount 90 Days Past Due and Accruing	0	0
Working capital [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
90 Days Past Due	0	0
Total Past Due	0	0
Current	1,758	1,726
Total Finance Receivables	1,758	1,726
Carrying Amount 90 Days Past Due and Accruing	$ 0	$ 0

[1]   Certain prior period amounts have been reclassified to conform to the current period presentation.