Finance Receivables, Net (Finance Receivable Credit Quality Indicators) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Mar. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Current	$ 64,791	$ 65,939
Financing receivables, past due	862	628
Total Finance Receivables	65,653	66,567
Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	50,621	49,684
Financing receivables, past due	862	618
Total Finance Receivables	51,483	50,302
Commercial Finance [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	0	511
Financing receivables, past due		10
Total Finance Receivables	0	521
Wholesale [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	7,792	9,226
Financing receivables, past due	0	0
Total Finance Receivables	7,792	9,226
Wholesale [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	6,913	7,993
Wholesale [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	794	1,137
Wholesale [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	67	60
Wholesale [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	18	36
Real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	4,613	4,665
Financing receivables, past due	0	0
Total Finance Receivables	4,613	4,665
Real estate [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	3,861	3,782
Real estate [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	676	842
Real estate [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	31	37
Real estate [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	45	4
Working capital [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	1,765	1,853
Financing receivables, past due	0	0
Total Finance Receivables	1,765	1,853
Working capital [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	1,564	1,643
Working capital [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	166	176
Working capital [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	30	32
Working capital [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	5	2
30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	631	475
30-59 Days Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	631	467
30-59 Days Past Due [Member] | Commercial Finance [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	0	8
30-59 Days Past Due [Member] | Wholesale [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	0	0
30-59 Days Past Due [Member] | Real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	0	0
30-59 Days Past Due [Member] | Working capital [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	0	0
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	154	102
60-89 Days Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	154	100
60-89 Days Past Due [Member] | Commercial Finance [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	0	2
60-89 Days Past Due [Member] | Wholesale [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	0	0
60-89 Days Past Due [Member] | Real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	0	0
60-89 Days Past Due [Member] | Working capital [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	0	0
90 Days or Greater Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	77	51
90 Days or Greater Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	77	51
90 Days or Greater Past Due [Member] | Commercial Finance [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	0	0
90 Days or Greater Past Due [Member] | Wholesale [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	0	0
90 Days or Greater Past Due [Member] | Real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	0	0
90 Days or Greater Past Due [Member] | Working capital [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	$ 0	$ 0