Finance Receivables, Net (Credit Quality Indicator) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Mar. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Current	$ 65,419	$ 65,180
30-59 Days Past Due	570	469
60-89 Days Past Due	126	92
90 Days or Greater Past Due	45	33
Total Finance Receivables	66,160	65,774
Wholesale [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	8,309	9,436
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
90 Days or Greater Past Due	0	0
Total Finance Receivables	8,309	9,436
Wholesale [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	7,188	8,129
Wholesale [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	1,102	1,282
Wholesale [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	19	24
Wholesale [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	0	1
Real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	4,641	4,653
30-59 Days Past Due	0	4
60-89 Days Past Due	0	1
90 Days or Greater Past Due	0	0
Total Finance Receivables	4,641	4,658
Real estate [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	3,774	3,791
Real estate [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	852	855
Real estate [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	11	12
Real estate [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	4	0
Working capital [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	2,003	1,831
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
90 Days or Greater Past Due	0	0
Total Finance Receivables	2,003	1,831
Working capital [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	1,834	1,642
Working capital [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	146	158
Working capital [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	23	25
Working capital [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	0	6
Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	49,993	48,828
30-59 Days Past Due	563	459
60-89 Days Past Due	125	90
90 Days or Greater Past Due	45	33
Total Finance Receivables	50,726	49,410
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	473	432
30-59 Days Past Due	7	6
60-89 Days Past Due	1	1
90 Days or Greater Past Due	0	0
Total Finance Receivables	$ 481	$ 439