Related Party Transactions - Related Party Transactions Included in Consolidated Statements of Income (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Net financing revenues:
Depreciation on operating leases		$ (1,900)	$ (1,712)	$ (1,583)	$ (1,625)	$ (1,764)	$ (1,717)	$ (1,662)	$ (1,766)	$ (6,820)	$ (6,909)	$ (7,041)
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues		241	231	232	229	228	226	226	224	933	904	882
Expenses:
Operating and administrative expenses		$ 460	$ 406	$ 358	$ 337	$ 366	$ 347	$ 348	$ 324	1,561	1,385	1,357
TMCC-affiliated companies [Member]
Net financing revenues:
Manufacturer's subvention and other revenues										2,065	1,930	1,590
Depreciation on operating leases										(59)	(24)	(12)
Interest expense:
Credit support fees, interest and other expenses										96	96	95
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues										181	181	182
Investment and other income, net:
Interest and other income										26	16	13
Expenses:
Operating and administrative expenses										102	95	80
Insurance losses and loss adjustment expenses	[1]									$ 0	$ (3)	$ (3)

[1] Amount includes the transfer of insurance losses and loss adjustment expenses under a reinsurance contract.