Related Party Transactions - Related Party Transactions Included in Consolidated Statements of Income (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Net financing revenues:
Depreciation on operating leases		$ (1,764)	$ (1,717)	$ (1,662)	$ (1,766)	$ (1,863)	$ (1,778)	$ (1,719)	$ (1,681)	$ (6,909)	$ (7,041)	$ (6,853)
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues		228	226	226	224	225	220	221	216	904	882	804
Expenses:
Operating and administrative expenses		$ 366	$ 347	$ 348	$ 324	$ 384	$ 323	$ 337	$ 313	1,385	1,357	1,277
TMCC-affiliated companies [Member]
Net financing revenues:
Manufacturers’ subvention and other revenues										1,930	1,590	1,374
Depreciation on operating leases										(24)	(12)	0
Interest expense:
Credit support fees, interest and other expenses										96	95	95
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues										181	182	149
Investment and other income, net:
Interest and other income										16	13	9
Expenses:
Operating and administrative expenses										95	80	73
Insurance losses and loss adjustment expenses	[1]									$ (3)	$ (3)	$ 0

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