Finance Receivables, Net - Aging of Amortized Cost Basis of Finance Receivables by Class (Details) - USD ($) $ in Millions	Sep. 30, 2024	Mar. 31, 2024
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	$ 104,893	$ 103,306
90 Days or greater past due and accruing	173	142
30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	1,788	1,602
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	554	451
90 Days or Greater Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	265	210
Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	2,607	2,263
Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	102,286	101,043
Retail Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	88,513	87,125
90 Days or greater past due and accruing	173	142
Retail Loan [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	1,762	1,602
Retail Loan [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	554	451
Retail Loan [Member] | 90 Days or Greater Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	265	210
Retail Loan [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	2,581	2,263
Retail Loan [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	85,932	84,862
Wholesale [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	6,360	6,673
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 Finance receivables	1	0
Wholesale [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	0	0
Wholesale [Member] | 90 Days or Greater Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	0	0
Wholesale [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	1	0
Wholesale [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	6,359	6,673
Real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	5,209	4,894
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 Finance receivables	0	0
Real estate [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	0	0
Real estate [Member] | 90 Days or Greater Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	0	0
Real estate [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	0	0
Real estate [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	5,209	4,894
Working capital [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	4,811	4,614
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 Finance receivables	25	0
Working capital [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	0	0
Working capital [Member] | 90 Days or Greater Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	0	0
Working capital [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	25	0
Working capital [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance receivables	$ 4,786	$ 4,614