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Investment Securities - Additional Information (Details)
 3 Months Ended 9 Months Ended
Sep. 30, 2024
USD ($)
security
Sep. 30, 2023
USD ($)
Sep. 30, 2024
USD ($)
security
Sep. 30, 2023
USD ($)
Dec. 31, 2023
USD ($)
Summary of Investment Holdings [Line Items]          
Transferred from available-for-sale to held-for-maturity $ 114,200,000   $ 114,200,000   $ 127,600,000
Allowance for credit losses for available-for-sale debt securities $ 0   $ 0   $ 0
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration] Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest   Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest   Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest
Allowance for securities held-to-maturity $ 150,000   $ 150,000   $ 150,000
Accrued interest receivable $ 42,500,000   $ 42,500,000   50,300,000
Number of securities in security portfolio | security 3,013   3,013    
Number of securities in unrealized loss position | security 2,452   2,452    
Equity securities, at fair value $ 89,249,000   $ 89,249,000   80,372,000
(Losses) gains on equity securities 1,500,000 $ (800,000) 1,400,000 $ (1,400,000)  
Impairments on equity securities without readily determinable fair value     0 0  
Downward adjustments on equity securities without readily determinable fair value     0 $ 0  
Other Assets          
Summary of Investment Holdings [Line Items]          
Equity securities without readily determinable fair value 580,300,000   580,300,000   449,300,000
Other Assets | Partnership Interest          
Summary of Investment Holdings [Line Items]          
Equity securities without readily determinable fair value 292,600,000   292,600,000   252,200,000
Other Assets | Initiatives in Low-to-Moderate Income Neighborhoods          
Summary of Investment Holdings [Line Items]          
Equity securities without readily determinable fair value $ 287,700,000   $ 287,700,000   $ 197,100,000