Related Party Transactions - Related Party Transactions Included in Consolidated Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Voluntary protection contract revenues and insurance earned premiums:
Voluntary protection contract revenues and insurance earned premiums	$ 263	$ 254	$ 522	$ 503
Expenses:
Operating and administrative	444	385	850	769
TMCC-affiliated companies [Member]
Net financing revenues:
Manufacturer's subvention and other revenues	316	457	655	936
Depreciation on operating leases	34	(25)	56	(53)
Interest expense:
Credit support fees, interest and other expenses	24	27	47	51
Voluntary protection contract revenues and insurance earned premiums:
Voluntary protection contract revenues and insurance earned premiums	39	43	79	85
Investment and other income, net:
Interest and other income	3	2	(3)	5
Expenses:
Operating and administrative	$ 16	$ 22	$ 37	$ 43