Finance Receivables, Net - Aging of Amortized Cost Basis of Finance Receivables by Class (Details) - USD ($) $ in Millions	Jun. 30, 2021	Mar. 31, 2021
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 883	$ 775
Current	78,764	79,595
Total Finance receivables	79,647	80,370
90 Days or greater past due and accruing	40	39
30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	630	562
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	180	144
90 Days or Greater Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	73	69
Retail Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	883	775
Current	67,978	65,953
Total Finance receivables	68,861	66,728
90 Days or greater past due and accruing	40	39
Retail Loan [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	630	562
Retail Loan [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	180	144
Retail Loan [Member] | 90 Days or Greater Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	73	69
Wholesale [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Current	3,580	6,157
Total Finance receivables	3,580	6,157
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	0
Current	5,094	5,203
Total Finance receivables	5,094	5,203
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	0
Working capital [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Current	2,112	2,282
Total Finance receivables	2,112	2,282
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