v3.25.2
Debt - Narrative (Detail) - USD ($)
12 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2023
Aug. 31, 2024
Debt Instrument [Line Items]        
Outstanding principal balance of long-term debt with floating interest rates $ 9,700,000,000 $ 7,700,000,000    
Outstanding principal balance of long-term debt with fixed interest rates 42,700,000,000 36,900,000,000    
Short-term debt 10,100,000,000 6,300,000,000    
Related party debt        
Debt Instrument [Line Items]        
Related party debt 11,000,000 0 $ 0  
AHFC | Syndicated Bank Credit Facilities        
Debt Instrument [Line Items]        
Maximum funds available (up to) 7,000,000,000.0      
Line of credit facility outstanding amount 0      
AHFC | Syndicated Bank Credit Facilities With 364 Day Credit Agreement        
Debt Instrument [Line Items]        
Maximum funds available (up to) 3,500,000,000      
AHFC | Syndicated Bank Credit Facilities With Three Year Credit Agreement        
Debt Instrument [Line Items]        
Maximum funds available (up to) 2,100,000,000      
AHFC | Syndicated Bank Credit Facilities With Five Year Credit Agreement        
Debt Instrument [Line Items]        
Maximum funds available (up to) 1,400,000,000      
AHFC | Other Credit Agreements        
Debt Instrument [Line Items]        
Maximum funds available (up to) 1,000,000,000.0      
Line of credit facility outstanding amount 0      
HCFI | Syndicated Bank Credit Facilities        
Debt Instrument [Line Items]        
Maximum funds available (up to) 1,400,000,000      
Line of credit facility outstanding amount 0      
HCFI | Syndicated Bank Credit Facilities With One Year Revolving Term        
Debt Instrument [Line Items]        
Maximum funds available (up to) 695,000,000      
HCFI | Syndicated Bank Credit Facilities With Five Year Revolving Term        
Debt Instrument [Line Items]        
Maximum funds available (up to) 695,000,000      
Commercial paper        
Debt Instrument [Line Items]        
Maximum funds available (up to) $ 8,700,000,000 $ 8,800,000,000    
Debt instrument, term 1 year 1 year    
Average outstanding balance $ 5,900,000,000 $ 6,600,000,000    
Commercial paper | Other Credit Agreements        
Debt Instrument [Line Items]        
Maximum balance outstanding at any month-end $ 7,400,000,000 $ 7,200,000,000    
Public MTN program        
Debt Instrument [Line Items]        
Maximum funds available (up to)       $ 45,000,000,000.0