Selected Quarterly Financial Data (Unaudited) - Summary of the Effects of the Change in Accounting Principle (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2022
Selected Quarterly Financial Information [Abstract]
Total financing revenues	$ 3,156	$ 3,098	$ 2,986	$ 2,904	$ 12,144	$ 11,293	$ 11,920
Depreciation on operating leases	1,062	1,044	918	1,155	4,179	5,122	5,846
Interest expense	1,304	1,230	1,272	899	4,705	3,054	1,401
Net financing revenues	790	824	796	850	3,260	3,117	4,673
Voluntary protection contract revenues and insurance earned premiums	289	282	278	271	1,120	1,053	1,015
Investment and other income, net	234	495	(18)	162	873	97	(26)
Net financing revenues and other revenues	1,313	1,601	1,056	1,283	5,253	4,267	5,662
Total expenses	911	866	815	759	3,351	2,959	2,338
Income before income taxes	402	735	241	524	1,902	1,308	3,324
Provision for income taxes	73	174	63	132	442	329	789
Net income	$ 329	$ 561	$ 178	$ 392	$ 1,460	$ 979	$ 2,535