Finance Receivables, Net (Finance Receivable Credit Quality Indicators) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Mar. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Current	$ 67,650	$ 65,489
Financing receivables, past due	1,139	773
Total Finance Receivables	68,789	66,262
Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	50,431	49,590
Financing receivables, past due	1,139	773
Total Finance Receivables	51,570	50,363
Wholesale [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	10,339	9,262
Financing receivables, past due	0	0
Total Finance Receivables	10,339	9,262
Wholesale [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	9,100	8,099
Wholesale [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	1,140	1,041
Wholesale [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	90	113
Wholesale [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	9	9
Real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	4,736	4,704
Financing receivables, past due	0	0
Total Finance Receivables	4,736	4,704
Real estate [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	3,981	3,822
Real estate [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	660	763
Real estate [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	85	109
Real estate [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	10	10
Working capital [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	2,144	1,933
Financing receivables, past due	0	0
Total Finance Receivables	2,144	1,933
Working capital [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	1,952	1,686
Working capital [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	181	229
Working capital [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	11	17
Working capital [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	0	1
30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	850	584
30-59 Days Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	850	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	0	0
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	204	129
60-89 Days Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	204	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	85	60
90 Days or Greater Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	85	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