Finance Receivables, Net (Credit Quality Indicator) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Mar. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Current	$ 64,156	$ 62,593
30-59 Days Past Due	537	460
60-89 Days Past Due	114	88
90 Days Past Due	36	31
Total Finance Receivables	64,843	63,172
Wholesale [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	8,557	8,689
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
90 Days Past Due	0	0
Total Finance Receivables	8,557	8,689	[1]
Wholesale [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	7,863	7,740	[1]
Wholesale [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	659	915	[1]
Wholesale [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	34	33	[1]
Wholesale [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	1	1	[1]
Real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	4,574	4,580
30-59 Days Past Due	5	0
60-89 Days Past Due	0	0
90 Days Past Due	0	0
Total Finance Receivables	4,579	4,580
Real estate [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	4,071	3,968
Real estate [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	485	583
Real estate [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	23	28
Real estate [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	0	1
Working capital [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	1,721	1,726
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
90 Days Past Due	0	0
Total Finance Receivables	1,721	1,726
Working capital [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	1,598	1,616
Working capital [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	90	80
Working capital [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	27	28
Working capital [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	6	2
Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	48,916	47,236
30-59 Days Past Due	526	454
60-89 Days Past Due	113	87
90 Days Past Due	36	31
Total Finance Receivables	49,591	47,808
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	388	362
30-59 Days Past Due	6	6
60-89 Days Past Due	1	1
90 Days Past Due	0	0
Total Finance Receivables	$ 395	$ 369

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