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Regulatory capital requirements - Additional Information (Details)
Dec. 31, 2021
USD ($)
Dec. 31, 2020
USD ($)
Regulatory Capital Requirements under Banking Regulations    
Loans held-in-portfolio $ 29,506,225,000 $ 29,588,430,000
Paycheck Protection Program    
Regulatory Capital Requirements under Banking Regulations    
Collateral loans 0  
SBA loans under PPP program    
Regulatory Capital Requirements under Banking Regulations    
Loans held-in-portfolio $ 353,000,000 $ 1,300,000,000
Standardized approach | Basel III    
Regulatory Capital Requirements under Banking Regulations    
CET 1 minimum ratio required ratio 0.065  
Tier one risk based capital required for capital adequacy ratio 0.08  
Capital required for capital adequacy ratio 0.10  
Leverage ratio required 0.05