Finance Receivables, Net (Credit Quality Indicator) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Mar. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Current	$ 59,839	$ 58,058
30-59 Days Past Due	489	442
60-89 Days Past Due	112	82
90 Days Past Due	35	29
Total Finance Receivables	60,475	58,611
Wholesale [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	8,028	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	8,028	7,008
Wholesale [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	7,005	6,249
Wholesale [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	906	675
Wholesale [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	108	78
Wholesale [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	9	6
Real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	4,405	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	4,405	4,361
Real estate [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	3,658	3,746
Real estate [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	591	467
Real estate [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	155	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	1,658	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	1,658	1,496
Working capital [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	1,532	1,422
Working capital [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	87	61
Working capital [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	32	8
Working capital [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	7	5
Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	45,401	44,842
30-59 Days Past Due	479	433
60-89 Days Past Due	110	80
90 Days Past Due	34	28
Total Finance Receivables	46,024	45,383
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	347	352
30-59 Days Past Due	10	8
60-89 Days Past Due	2	2
90 Days Past Due	1	1
Total Finance Receivables	$ 360	$ 363