Fair Value Measurements - Assets and Liabilities Not Carried at Fair Value on Recurring Basis on Consolidated Balance Sheets (Details) - USD ($) $ in Millions	Sep. 30, 2023	Mar. 31, 2023
Fair value [Member] | Unsecured Notes and Loans Payable [Member]
Financial liabilities
Financial liabilities	$ 77,391	$ 76,401
Fair value [Member] | Secured Notes and Loans Payable [Member]
Financial liabilities
Financial liabilities	31,971	32,173
Fair value [Member] | Level 1 [Member] | Unsecured Notes and Loans Payable [Member]
Financial liabilities
Financial liabilities	0	0
Fair value [Member] | Level 1 [Member] | Secured Notes and Loans Payable [Member]
Financial liabilities
Financial liabilities	0	0
Fair value [Member] | Level 2 [Member] | Unsecured Notes and Loans Payable [Member]
Financial liabilities
Financial liabilities	77,391	76,401
Fair value [Member] | Level 2 [Member] | Secured Notes and Loans Payable [Member]
Financial liabilities
Financial liabilities	0	0
Fair value [Member] | Level 3 [Member] | Unsecured Notes and Loans Payable [Member]
Financial liabilities
Financial liabilities	0	0
Fair value [Member] | Level 3 [Member] | Secured Notes and Loans Payable [Member]
Financial liabilities
Financial liabilities	31,971	32,173
Carrying value [Member] | Unsecured Notes and Loans Payable [Member]
Financial liabilities
Financial liabilities	80,430	78,949
Carrying value [Member] | Secured Notes and Loans Payable [Member]
Financial liabilities
Financial liabilities	32,596	32,736
Retail Loan [Member] | Fair value [Member]
Financial assets
Finance receivables, net	81,844	77,649
Retail Loan [Member] | Fair value [Member] | Level 1 [Member]
Financial assets
Finance receivables, net	0	0
Retail Loan [Member] | Fair value [Member] | Level 2 [Member]
Financial assets
Finance receivables, net	0	0
Retail Loan [Member] | Fair value [Member] | Level 3 [Member]
Financial assets
Finance receivables, net	81,844	77,649
Retail Loan [Member] | Carrying value [Member]
Financial assets
Finance receivables, net	82,938	78,445
Wholesale [Member] | Fair value [Member]
Financial assets
Finance receivables, net	5,568	3,968
Wholesale [Member] | Fair value [Member] | Level 1 [Member]
Financial assets
Finance receivables, net	0	0
Wholesale [Member] | Fair value [Member] | Level 2 [Member]
Financial assets
Finance receivables, net	0	0
Wholesale [Member] | Fair value [Member] | Level 3 [Member]
Financial assets
Finance receivables, net	5,568	3,968
Wholesale [Member] | Carrying value [Member]
Financial assets
Finance receivables, net	5,562	3,972
Real estate [Member] | Fair value [Member]
Financial assets
Finance receivables, net	4,777	4,990
Real estate [Member] | Fair value [Member] | Level 1 [Member]
Financial assets
Finance receivables, net	0	0
Real estate [Member] | Fair value [Member] | Level 2 [Member]
Financial assets
Finance receivables, net	0	0
Real estate [Member] | Fair value [Member] | Level 3 [Member]
Financial assets
Finance receivables, net	4,777	4,990
Real estate [Member] | Carrying value [Member]
Financial assets
Finance receivables, net	4,871	4,981
Working capital [Member] | Fair value [Member]
Financial assets
Finance receivables, net	3,328	3,058
Working capital [Member] | Fair value [Member] | Level 1 [Member]
Financial assets
Finance receivables, net	0	0
Working capital [Member] | Fair value [Member] | Level 2 [Member]
Financial assets
Finance receivables, net	0	0
Working capital [Member] | Fair value [Member] | Level 3 [Member]
Financial assets
Finance receivables, net	3,328	3,058
Working capital [Member] | Carrying value [Member]
Financial assets
Finance receivables, net	$ 3,417	$ 3,113