Finance Receivables, Net (Finance Receivable Credit Quality Indicators) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Mar. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Current	$ 68,527	$ 65,489
Financing receivables, past due	781	773
Total Finance Receivables	69,308	66,262
Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	50,631	49,590
Financing receivables, past due	778	773
Total Finance Receivables	51,409	50,363
Wholesale [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	10,951	9,262
Financing receivables, past due	0	0
Total Finance Receivables	10,951	9,262
Wholesale [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	9,592	8,099
Wholesale [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	1,269	1,041
Wholesale [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	12	113
Wholesale [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	78	9
Real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	4,713	4,704
Financing receivables, past due	0	0
Total Finance Receivables	4,713	4,704
Real estate [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	4,010	3,822
Real estate [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	613	763
Real estate [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	45	109
Real estate [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	45	10
Working capital [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	2,232	1,933
Financing receivables, past due	3	0
Total Finance Receivables	2,235	1,933
Working capital [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	2,082	1,686
Working capital [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	143	229
Working capital [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	5	17
Working capital [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	5	1
30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	589	584
30-59 Days Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	586	584
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	3	0
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	129	129
60-89 Days Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	129	129
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	63	60
90 Days or Greater Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	63	60
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