Allowance for Credit Losses (Past Dues) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Mar. 31, 2012
Past Due Finance Receivables and Investments in Operating Leases
Finance receivables	$ 147	$ 111
Operating leases	35	31
Total	182	142
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	489	442
60-89 Days Past Due	112	82
90 Days Past Due	35	29
Total Past Due	636	553
Current	59,839	58,058
Total Finance Receivables	60,475	58,611
Carrying Amount 90 Days Past Due and Accruing	35	29
Retail Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	479	433
60-89 Days Past Due	110	80
90 Days Past Due	34	28
Total Past Due	623	541
Current	45,401	44,842
Total Finance Receivables	46,024	45,383
Carrying Amount 90 Days Past Due and Accruing	34	28
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	10	8
60-89 Days Past Due	2	2
90 Days Past Due	1	1
Total Past Due	13	11
Current	347	352
Total Finance Receivables	360	363
Carrying Amount 90 Days Past Due and Accruing	1	1
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	8,028	7,008
Total Finance Receivables	8,028	7,008
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	0	0
60-89 Days Past Due	0	0
90 Days Past Due	0	0
Total Past Due	0	0
Current	4,405	4,361
Total Finance Receivables	4,405	4,361
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	1
60-89 Days Past Due	0	0
90 Days Past Due	0	0
Total Past Due	0	1
Current	1,658	1,495
Total Finance Receivables	1,658	1,496
Carrying Amount 90 Days Past Due and Accruing	$ 0	$ 0