Finance Receivables, Net (Credit Quality Indicator) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Current	$ 62,593	$ 58,058
30-59 Days Past Due	460	442
60-89 Days Past Due	88	82
90 Days Past Due	31	29
Total Finance Receivables	63,172	58,611
Wholesale [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	8,689	7,008
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
90 Days Past Due	0	0
Total Finance Receivables	8,689	7,008
Wholesale [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	7,659	6,249
Wholesale [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	996	675
Wholesale [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	33	78
Wholesale [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	1	6
Real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	4,580	4,361
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
90 Days Past Due	0	0
Total Finance Receivables	4,580	4,361
Real estate [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	3,968	3,746
Real estate [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	583	467
Real estate [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	28	148
Real estate [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	1	0
Working capital [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	1,726	1,495
30-59 Days Past Due	0	1
60-89 Days Past Due	0	0
90 Days Past Due	0	0
Total Finance Receivables	1,726	1,496
Working capital [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	1,616	1,422
Working capital [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	80	61
Working capital [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	28	8
Working capital [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	2	5
Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	47,236	44,842
30-59 Days Past Due	454	433
60-89 Days Past Due	87	80
90 Days Past Due	31	28
Total Finance Receivables	47,808	45,383
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	362	352
30-59 Days Past Due	6	8
60-89 Days Past Due	1	2
90 Days Past Due	0	1
Total Finance Receivables	$ 369	$ 363