v3.26.3
Fair Value Measurement - Estimates Fair Value of Financial Instruments (Detail) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Financial Assets    
Cash and due from banks $ 978,860 $ 956,109
Equity securities 18,303 30,809
Available-for-sale debt securities 3,353,692 3,288,332
Net held-to-maturity debt securities 1,094,139 1,132,114
Net loans 19,685,993 19,007,683
Accrued interest receivable 106,182 106,651
Financial Liabilities    
Deposits 21,612,503 21,668,840
Federal Home Loan Bank borrowings 1,950,000 1,200,000
Other borrowings 113,800 110,679
Subordinated debt and junior subordinated debt 308,991 308,529
Accrued interest payable 21,363 19,150
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]    
Financial Assets    
Cash and due from banks 978,860 956,109
Accrued interest receivable 106,182 106,651
Financial Liabilities    
Deposits 19,105,584 18,793,468
Other borrowings 104,171 105,240
Accrued interest payable 21,363 19,150
Significant Other Observable Inputs (Level 2) [Member]    
Financial Assets    
Net held-to-maturity debt securities 924,101 1,035,821
Financial Liabilities    
Deposits 2,487,456 2,863,653
Federal Home Loan Bank borrowings 1,942,923 1,200,761
Subordinated debt and junior subordinated debt 301,104 298,974
Significant Unobservable Inputs (Level 3) [Member]    
Financial Assets    
Net held-to-maturity debt securities 102 136
Net loans 19,332,186 18,563,341
Loans held for sale 20,440  
Carrying Amount [Member]    
Financial Assets    
Cash and due from banks 978,860 956,109
Net held-to-maturity debt securities 1,093,970 1,131,946
Net loans 19,685,993 19,007,683
Loans held for sale 19,162  
Accrued interest receivable 106,182 106,651
Financial Liabilities    
Deposits 21,612,503 21,668,840
Federal Home Loan Bank borrowings 1,950,000 1,200,000
Other borrowings 113,800 110,679
Subordinated debt and junior subordinated debt 308,991 308,529
Accrued interest payable 21,363 19,150
Fair Value Estimate [Member]    
Financial Assets    
Cash and due from banks 978,860 956,109
Net held-to-maturity debt securities 924,203 1,035,957
Net loans 19,332,186 18,563,341
Loans held for sale 20,440  
Accrued interest receivable 106,182 106,651
Financial Liabilities    
Deposits 21,593,040 21,657,121
Federal Home Loan Bank borrowings 1,942,923 1,200,761
Other borrowings 104,171 105,240
Subordinated debt and junior subordinated debt 301,104 298,974
Accrued interest payable $ 21,363 $ 19,150