Finance Receivables, Net - Finance Receivable Credit Quality Indicators (Details) - USD ($) $ in Millions	Mar. 31, 2020	Mar. 31, 2019
Financing Receivable, Recorded Investment [Line Items]
Current	$ 73,936	$ 70,738
Financing receivables, past due	1,025	897
Total Finance Receivables	74,961	71,635
Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	56,064	53,047
Financing receivables, past due	1,024	892
Total Finance Receivables	57,088	53,939
Wholesale [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	9,826	10,439
Financing receivables, past due	0	1
Total Finance Receivables	9,826	10,440
Wholesale [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	8,750	9,155
Wholesale [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	962	1,127
Wholesale [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	92	152
Wholesale [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	22	6
Real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	4,627	4,671
Financing receivables, past due	1	0
Total Finance Receivables	4,628	4,671
Real estate [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	3,974	4,019
Real estate [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	576	554
Real estate [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	55	84
Real estate [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	23	14
Working capital [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	3,419	2,581
Financing receivables, past due	0	4
Total Finance Receivables	3,419	2,585
Working capital [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	3,132	2,448
Working capital [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	195	70
Working capital [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	92	63
Working capital [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Finance Receivables	0	4
30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	717	657
30-59 Days Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	717	657
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	203	162
60-89 Days Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	203	162
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	105	78
90 Days or Greater Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	104	73
90 Days or Greater Past Due [Member] | Wholesale [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	0	1
90 Days or Greater Past Due [Member] | Real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	1	0
90 Days or Greater Past Due [Member] | Working capital [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables, past due	$ 0	$ 4