Related Party Transactions - Related Party Transactions Included in Consolidated Balance Sheets (Details) - USD ($) $ in Millions	Mar. 31, 2025	Mar. 31, 2024
Cash and cash equivalents
Cash and cash equivalents	$ 10,769	$ 8,570
Investments in marketable securities
Investments in marketable securities	4,581	4,505
Other assets
Notes receivable	101,749	101,669
Other liabilities
Other payables, net	7,333	6,707
TMCC-affiliated companies [Member]
Finance receivables, net
Accounts receivable	73	49
Deferred retail subvention income	(1,170)	(953)
Investments in operating leases, net
Investments in operating leases, net	(100)	(80)
Deferred lease subvention income	(500)	(323)
Other assets
Notes receivable	2,651	1,724
Other receivables, net	96	86
Other liabilities
Unearned voluntary protection contract revenues and insurance earned premiums	486	433
Other payables, net	831	771
Notes payable	15	8
Commercial paper [Member] | TMCC-affiliated companies [Member]
Investments in marketable securities
Investments in marketable securities	$ 15	$ 0