v3.26.3
Fair Value - Estimated fair value and related carrying amount, of the Company's financial instruments (Details) - USD ($)
$ in Thousands
 9 Months Ended 12 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Dec. 31, 2025
Financial assets:      
Trading securities $ 141,534   $ 110,183
Financial liabilities:      
Other derivative financial instruments (mortgage banking related) 433,212 $ (325,835)  
Carrying Amount      
Financial assets:      
Cash and cash equivalents 2,974,618   3,172,483
Trading securities 141,534   110,183
Investment securities 8,705,780   8,715,214
Loans held for sale 296,835   345,343
Loans, net of allowance for credit losses 51,464,175   48,013,330
Accrued interest receivable 253,452   233,265
Mortgage servicing rights 101,990   84,032
SBA servicing asset 4,748   5,512
Interest rate swap - non-designated hedge 117,921   221,835
Other derivative financial instruments (mortgage banking related) $ 1,810   $ 1,051
Derivative Asset, Statement of Financial Position [Extensible Enumeration] Derivative Asset, Noncurrent   Derivative Asset, Noncurrent
Financial liabilities:      
Noninterest-bearing $ 13,445,715   $ 13,375,697
Interest-bearing other than time deposits 35,840,527   34,410,867
Time deposits 8,352,039   7,359,233
Federal funds purchased and securities sold under agreements to repurchase 498,173   618,215
Corporate and subordinated debentures 696,855   696,536
Other borrowings 300,000    
Accrued interest payable 37,494   48,972
Interest rate swap - non-designated hedge 982,452   554,433
Other derivative financial instruments (mortgage banking related) 5,508   315
Fair Value      
Financial assets:      
Cash and cash equivalents 2,974,618   3,172,483
Trading securities 141,534   110,183
Investment securities 8,319,757   8,400,034
Loans held for sale 297,162   348,381
Loans, net of allowance for credit losses 50,926,865   47,378,022
Accrued interest receivable 253,452   233,265
Mortgage servicing rights 101,990   84,032
SBA servicing asset 4,748   5,512
Interest rate swap - non-designated hedge 117,921   221,835
Other derivative financial instruments (mortgage banking related) 1,810   1,051
Financial liabilities:      
Noninterest-bearing 13,445,715   13,375,697
Interest-bearing other than time deposits 35,840,527   34,410,867
Time deposits 8,323,116   7,347,648
Federal funds purchased and securities sold under agreements to repurchase 498,173   618,215
Corporate and subordinated debentures 678,415   683,772
Other borrowings 299,994    
Accrued interest payable 37,494   48,972
Interest rate swap - non-designated hedge 982,452   554,433
Other derivative financial instruments (mortgage banking related) 5,508   315
Quoted Prices In Active Markets for Identical Assets (Level 1)      
Financial assets:      
Cash and cash equivalents 2,974,618   3,172,483
Investment securities 287,005   274,730
Significant Other Observable Inputs (Level 2)      
Financial assets:      
Trading securities 141,534   110,183
Investment securities 7,912,585   8,046,606
Loans held for sale 297,162   348,381
Accrued interest receivable 35,312   35,302
Interest rate swap - non-designated hedge 117,921   221,835
Other derivative financial instruments (mortgage banking related) 1,810   1,051
Financial liabilities:      
Noninterest-bearing 13,445,715   13,375,697
Interest-bearing other than time deposits 35,840,527   34,410,867
Time deposits 8,323,116   7,347,648
Federal funds purchased and securities sold under agreements to repurchase 498,173   618,215
Corporate and subordinated debentures 678,415   683,772
Other borrowings 299,994    
Accrued interest payable 37,494   48,972
Interest rate swap - non-designated hedge 982,452   554,433
Other derivative financial instruments (mortgage banking related) 5,508   315
Significant Unobservable Inputs (Level 3)      
Financial assets:      
Investment securities 120,167   78,698
Loans, net of allowance for credit losses 50,926,865   47,378,022
Accrued interest receivable 218,140   197,963
Mortgage servicing rights 101,990   84,032
SBA servicing asset $ 4,748   $ 5,512