v3.26.1
Debt - Narrative (Detail) - USD ($)
3 Months Ended 12 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Mar. 31, 2026
Aug. 31, 2025
Debt Instrument [Line Items]        
Outstanding principal balance of long-term debt with floating interest rates $ 11,700,000,000   $ 14,200,000,000  
Outstanding principal balance of long-term debt with fixed interest rates 47,400,000,000   46,700,000,000  
Short-term debt 6,200,000,000   4,100,000,000  
Related Party        
Debt Instrument [Line Items]        
Related party debt 0 $ 20,000,000    
Other Credit Agreements | AHFC        
Debt Instrument [Line Items]        
Maximum funds available (up to) 1,000,000,000.0      
Line of credit facility outstanding amount 0      
Syndicated Bank Credit Facilities | AHFC        
Debt Instrument [Line Items]        
Maximum funds available (up to) 8,500,000,000      
Line of credit facility outstanding amount 0      
Syndicated Bank Credit Facilities | HCFI        
Debt Instrument [Line Items]        
Maximum funds available (up to) 1,400,000,000      
Line of credit facility outstanding amount 0      
Syndicated Bank Credit Facilities With 364 Day Credit Agreement | AHFC        
Debt Instrument [Line Items]        
Maximum funds available (up to) $ 2,800,000,000      
Debt instrument, term 364 days      
Syndicated Bank Credit Facilities With Three Year Credit Agreement | AHFC        
Debt Instrument [Line Items]        
Maximum funds available (up to) $ 2,800,000,000      
Syndicated Bank Credit Facilities With Five Year Credit Agreement | AHFC        
Debt Instrument [Line Items]        
Maximum funds available (up to) 2,800,000,000      
Syndicated Bank Credit Facilities With One Year Revolving Term | HCFI        
Debt Instrument [Line Items]        
Maximum funds available (up to) 704,000,000      
Syndicated Bank Credit Facilities With Five Year Revolving Term | HCFI        
Debt Instrument [Line Items]        
Maximum funds available (up to) 704,000,000      
Commercial paper        
Debt Instrument [Line Items]        
Maximum funds available (up to) $ 10,300,000,000   $ 10,300,000,000  
Debt instrument, term 1 year   1 year  
Average outstanding balance $ 4,000,000,000.0 6,600,000,000    
Commercial paper | Other Credit Agreements        
Debt Instrument [Line Items]        
Maximum balance outstanding at any month-end $ 5,600,000,000 $ 7,300,000,000    
Public MTN Program        
Debt Instrument [Line Items]        
Maximum funds available (up to)       $ 45,000,000,000.0