Finance Receivables, Net - Aging of Amortized Cost Basis of Finance Receivables by Class (Details) - USD ($) $ in Millions	Mar. 31, 2021	Mar. 31, 2020
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 775	$ 1,025
Current	79,595	73,936
Total Finance receivables	80,370	74,961
90 Days or greater past due and accruing	39	66
30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	562	717
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	144	203
90 Days or Greater Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	69	105
Retail Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	775	1,024
Current	65,953	56,064
Total Finance receivables	66,728	57,088
90 Days or greater past due and accruing	39	66
Retail Loan [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	562	717
Retail Loan [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	144	203
Retail Loan [Member] | 90 Days or Greater Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	69	104
Wholesale [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Current	6,157	9,826
Total Finance receivables	6,157	9,826
90 Days or greater past due and accruing	0	0
Wholesale [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Wholesale [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Wholesale [Member] | 90 Days or Greater Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	1
Current	5,203	4,627
Total Finance receivables	5,203	4,628
90 Days or greater past due and accruing	0	0
Real estate [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Real estate [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Real estate [Member] | 90 Days or Greater Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	1
Working capital [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Current	2,282	3,419
Total Finance receivables	2,282	3,419
90 Days or greater past due and accruing	0	0
Working capital [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Working capital [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Working capital [Member] | 90 Days or Greater Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 0	$ 0