v3.25.2
Debt - Narrative (Detail) - USD ($)
3 Months Ended 12 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Mar. 31, 2025
Aug. 31, 2024
Debt Instrument [Line Items]        
Outstanding principal balance of long-term debt with floating interest rates $ 11,000,000,000   $ 9,700,000,000  
Outstanding principal balance of long-term debt with fixed interest rates 43,700,000,000   42,700,000,000  
Related party debt 9,700,000,000   10,100,000,000  
Related Party        
Debt Instrument [Line Items]        
Related party debt 20,000,000 $ 0    
AHFC | Other Credit Agreements        
Debt Instrument [Line Items]        
Maximum funds available 1,000,000,000.0      
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 735,000,000      
HCFI | Syndicated Bank Credit Facilities With Five Year Revolving Term        
Debt Instrument [Line Items]        
Maximum funds available 735,000,000      
Commercial paper        
Debt Instrument [Line Items]        
Maximum funds available $ 8,800,000,000   $ 8,700,000,000  
Line of credit, term (up to) 1 year   1 year  
Average outstanding balance $ 6,600,000,000 5,400,000,000    
Commercial paper | Other Credit Agreements        
Debt Instrument [Line Items]        
Line of credit facility, maximum month-end outstanding amount $ 7,300,000,000 $ 6,100,000,000    
Public MTN program        
Debt Instrument [Line Items]        
Maximum funds available       $ 45,000,000,000