v3.25.4
Debt - Narrative (Detail) - USD ($)
3 Months Ended 9 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2025
Dec. 31, 2024
Aug. 31, 2025
Mar. 31, 2025
Debt Instrument [Line Items]            
Outstanding principal balance of long-term debt with floating interest rates $ 14,700,000,000   $ 14,700,000,000     $ 9,700,000,000
Outstanding principal balance of long-term debt with fixed interest rates 45,700,000,000   45,700,000,000     42,700,000,000
Related party debt 5,500,000,000   5,500,000,000     10,100,000,000
Related Party            
Debt Instrument [Line Items]            
Related party debt 0 $ 0 28,000,000 $ 0    
AHFC | Other Credit Agreements            
Debt Instrument [Line Items]            
Maximum funds available 1,000,000,000.0   1,000,000,000.0      
Line of credit facility outstanding amount 0   0      
AHFC | Syndicated Bank Credit Facilities            
Debt Instrument [Line Items]            
Maximum funds available 7,000,000,000   7,000,000,000      
Line of credit facility outstanding amount 0   0      
AHFC | Syndicated Bank Credit Facilities With 364 Day Credit Agreement            
Debt Instrument [Line Items]            
Maximum funds available 3,500,000,000   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   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   1,400,000,000      
HCFI | Syndicated Bank Credit Facilities            
Debt Instrument [Line Items]            
Maximum funds available 1,500,000,000   1,500,000,000      
Line of credit facility outstanding amount 0   0      
HCFI | Syndicated Bank Credit Facilities With One Year Revolving Term            
Debt Instrument [Line Items]            
Maximum funds available 729,000,000   729,000,000      
HCFI | Syndicated Bank Credit Facilities With Five Year Revolving Term            
Debt Instrument [Line Items]            
Maximum funds available 729,000,000   729,000,000      
Commercial paper            
Debt Instrument [Line Items]            
Maximum funds available $ 8,800,000,000   $ 8,800,000,000     $ 8,700,000,000
Line of credit, term (up to)     1 year      
Average outstanding balance     $ 5,700,000,000 5,600,000,000    
Commercial paper | Other Credit Agreements            
Debt Instrument [Line Items]            
Line of credit facility, maximum month-end outstanding amount     $ 7,300,000,000 $ 6,700,000,000    
Public MTN Program            
Debt Instrument [Line Items]            
Maximum funds available         $ 45,000,000,000