Debt - Narrative (Detail) - USD ($)	9 Months Ended		12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Mar. 31, 2023	Aug. 31, 2022
Debt Instrument [Line Items]
Outstanding principal balance of long-term debt with floating interest rates	$ 6,500,000,000		$ 4,100,000,000
Outstanding principal balance of long-term debt with fixed interest rates	34,100,000,000		29,500,000,000
Short-term debt	7,300,000,000		6,700,000,000
AHFC | Other Credit Agreements
Debt Instrument [Line Items]
Maximum funds available	1,000,000,000
Line of credit facility outstanding amount	0
AHFC | Syndicated Bank Credit Facilities
Debt Instrument [Line Items]
Maximum funds available	7,000,000,000
Line of credit facility outstanding amount	0
AHFC | Syndicated Bank Credit Facilities With 364 Day Credit Agreement
Debt Instrument [Line Items]
Maximum funds available	3,500,000,000
AHFC | Syndicated Bank Credit Facilities With Three Year Credit Agreement
Debt Instrument [Line Items]
Maximum funds available	2,100,000,000
AHFC | Syndicated Bank Credit Facilities With Five Year Credit Agreement
Debt Instrument [Line Items]
Maximum funds available	1,400,000,000
HCFI | Syndicated Bank Credit Facilities
Debt Instrument [Line Items]
Maximum funds available	1,500,000,000
Line of credit facility outstanding amount	0
HCFI | Syndicated Bank Credit Facilities With One Year Revolving Term
Debt Instrument [Line Items]
Maximum funds available	755,000,000
HCFI | Syndicated Bank Credit Facilities With Five Year Revolving Term
Debt Instrument [Line Items]
Maximum funds available	755,000,000
Commercial paper
Debt Instrument [Line Items]
Maximum funds available	$ 8,900,000,000		$ 8,800,000,000
Line of credit, term (up to)	1 year		1 year
Average outstanding balance	$ 6,700,000,000	$ 3,400,000,000
Commercial paper | Other Credit Agreements
Debt Instrument [Line Items]
Line of credit facility, maximum month-end outstanding amount	$ 7,200,000,000	$ 5,300,000,000
Public MTN program
Debt Instrument [Line Items]
Maximum funds available				$ 30,000,000,000