Allowance for Credit Losses (Past Dues) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Mar. 31, 2014
Past Due Finance Receivables and Investments in Operating Leases
Finance receivables	$ 171	$ 125
Operating leases	54	36
Total	225	161
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	570	469
60-89 Days Past Due	126	92
90 Days or Greater Past Due	45	33
Total Past Due	741	594
Current	65,419	65,180
Total Finance Receivables	66,160	65,774
90 Days or Greater Past Due and Accruing	45	33
Retail Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	563	459
60-89 Days Past Due	125	90
90 Days or Greater Past Due	45	33
Total Past Due	733	582
Current	49,993	48,828
Total Finance Receivables	50,726	49,410
90 Days or Greater Past Due and Accruing	45	33
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	7	6
60-89 Days Past Due	1	1
90 Days or Greater Past Due	0	0
Total Past Due	8	7
Current	473	432
Total Finance Receivables	481	439
90 Days or Greater 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 or Greater Past Due	0	0
Total Past Due	0	0
Current	8,309	9,436
Total Finance Receivables	8,309	9,436
90 Days or Greater Past Due and Accruing	0	0
Real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	0	4
60-89 Days Past Due	0	1
90 Days or Greater Past Due	0	0
Total Past Due	0	5
Current	4,641	4,653
Total Finance Receivables	4,641	4,658
90 Days or Greater 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 or Greater Past Due	0	0
Total Past Due	0	0
Current	2,003	1,831
Total Finance Receivables	2,003	1,831
90 Days or Greater Past Due and Accruing	$ 0	$ 0