v3.26.1
Related Party Transactions - Narrative (Details)
 3 Months Ended
Jun. 30, 2026
USD ($)
borrowing
Dec. 31, 2025
USD ($)
Related Party Transaction [Line Items]    
Long-term debt $ 25,305,000,000 $ 23,026,000,000
Loans receivable from related parties 62,103,000,000 59,894,000,000
Notional value of derivative contracts 1,717,600,000,000 1,405,200,000,000
Preferred stock issued 265,000,000 265,000,000
Payment of dividends on common stock 300,000,000  
HSBC Bank USA and its Subsidiaries    
Related Party Transaction [Line Items]    
Payment of dividends on common stock 300,000,000  
HNAH    
Related Party Transaction [Line Items]    
Long-term debt 12,100,000,000 10,100,000,000
Maximum borrowing capacity 4,300,000,000  
Amount outstanding under the loan agreement 0 0
Preferred stock issued 265,000,000 265,000,000
Preferred stock outstanding 265,000,000 265,000,000
HNAH | Loans And Lines Of Credit    
Related Party Transaction [Line Items]    
Loans receivable from related parties 3,200,000,000 4,200,000,000
HMUS | Loans And Lines Of Credit    
Related Party Transaction [Line Items]    
Extended loans and lines of credit 14,500,000,000 14,500,000,000
Loans receivable from related parties 3,200,000,000 1,800,000,000
Other HSBC affiliates | Loans And Lines Of Credit    
Related Party Transaction [Line Items]    
Extended loans and lines of credit 7,300,000,000  
Loans receivable from related parties 0 0
Related Party    
Related Party Transaction [Line Items]    
Long-term debt 12,138,000,000 10,137,000,000
Loans receivable from related parties 6,400,000,000 6,000,000,000.0
Notional value of derivative contracts 1,018,300,000,000 794,800,000,000
Fair value of derivative assets and liabilities 36,000,000 $ 228,000,000
Fixed Rate Note Maturing December 2027 | HNAH | Senior debt:    
Related Party Transaction [Line Items]    
Long-term debt 500,000,000  
Fixed Rate Note Maturing March 2028 | HNAH | Senior debt:    
Related Party Transaction [Line Items]    
Long-term debt 1,500,000,000  
Floating Rate Note Maturing March 2028 | HNAH | Senior debt:    
Related Party Transaction [Line Items]    
Long-term debt 750,000,000  
Fixed Rate Note Maturing December 2028 | HNAH | Senior debt:    
Related Party Transaction [Line Items]    
Long-term debt 500,000,000  
Fixed Rate Note Maturing September 2029 | HNAH | Senior debt:    
Related Party Transaction [Line Items]    
Long-term debt 1,000,000,000.0  
Floating Rate Note Maturing March 2030 | HNAH | Senior debt:    
Related Party Transaction [Line Items]    
Long-term debt 750,000,000  
Fixed Rate Note Maturing June 2030 | HNAH | Senior debt:    
Related Party Transaction [Line Items]    
Long-term debt 1,500,000,000  
Fixed Rate Note Maturing November 2026 to November 2032 | HNAH | Senior debt:    
Related Party Transaction [Line Items]    
Long-term debt $ 1,640,000,000  
Number of equal borrowings | borrowing 7  
Fixed Rate Note Maturing May 2035 | HNAH | Senior debt:    
Related Party Transaction [Line Items]    
Long-term debt $ 2,000,000,000.0  
Fixed Rate Note Maturing March 2029 | HNAH | Senior debt:    
Related Party Transaction [Line Items]    
Long-term debt $ 2,000,000,000.0