Related Party Transactions - Related Party Transactions Included in Consolidated Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2025	Dec. 31, 2024
Voluntary protection contract revenues and insurance earned premiums:
Voluntary protection contract revenues and insurance earned premiums	$ 334	$ 303	$ 982	$ 898
Expenses:
Operating and administrative	484	451	1,400	1,344
TMCC-affiliated companies [Member]
Net financing revenues:
Manufacturer's subvention and other revenues	294	252	850	716
Depreciation on operating leases	(3)	3	7	24
Interest expense:
Credit support fees, interest and other expenses	28	29	82	86
Voluntary protection contract revenues and insurance earned premiums:
Voluntary protection contract revenues and insurance earned premiums	44	48	150	131
Investment and other income, net:
Interest and other income (loss), net	40	(3)	144	45
Expenses:
Operating and administrative	$ 30	$ 26	$ 93	$ 78