v3.26.1
Investment Securities - Amortized Cost, Gross Unrealized Gains and Losses and Fair Value of Debt Securities Held to Maturity (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Mar. 31, 2026
Dec. 31, 2025
Jun. 30, 2025
Mar. 31, 2025
Dec. 31, 2024
Schedule of Held-to-maturity Securities [Line Items]            
Amortized Cost $ 3,757,944   $ 3,496,571      
Gross Unrealized Gains 5,878   11,616      
Gross Unrealized Losses (395,472)   (378,584)      
Fair Value 3,368,350   3,129,603      
Allowance for Credit Losses 744 $ 746 734 $ 637 $ 633 $ 647
Net Carrying Value 3,757,200   3,495,837      
U.S. government agency securities            
Schedule of Held-to-maturity Securities [Line Items]            
Amortized Cost 290,828   292,269      
Gross Unrealized Gains 24   19      
Gross Unrealized Losses (42,066)   (39,226)      
Fair Value 248,786   253,062      
Allowance for Credit Losses 0   0      
Net Carrying Value 290,828   292,269      
Obligations of states and state agencies            
Schedule of Held-to-maturity Securities [Line Items]            
Amortized Cost 57,749   60,801      
Gross Unrealized Gains 374   504      
Gross Unrealized Losses (3,438)   (3,293)      
Fair Value 54,685   58,012      
Allowance for Credit Losses 1   2      
Net Carrying Value 57,748   60,799      
Municipal bonds            
Schedule of Held-to-maturity Securities [Line Items]            
Amortized Cost 322,964   293,074      
Gross Unrealized Gains 38   43      
Gross Unrealized Losses (19,942)   (17,295)      
Fair Value 303,060   275,822      
Allowance for Credit Losses 200   134      
Net Carrying Value 322,764   292,940      
Obligations of states and political subdivisions            
Schedule of Held-to-maturity Securities [Line Items]            
Amortized Cost 380,713   353,875      
Gross Unrealized Gains 412   547      
Gross Unrealized Losses (23,380)   (20,588)      
Fair Value 357,745   333,834      
Allowance for Credit Losses 201   136      
Net Carrying Value 380,512   353,739      
Residential mortgage-backed securities            
Schedule of Held-to-maturity Securities [Line Items]            
Amortized Cost 2,973,477   2,732,752      
Gross Unrealized Gains 5,438   11,050      
Gross Unrealized Losses (324,397)   (311,815)      
Fair Value 2,654,518   2,431,987      
Allowance for Credit Losses 0   0      
Net Carrying Value 2,973,477   2,732,752      
Trust preferred securities            
Schedule of Held-to-maturity Securities [Line Items]            
Amortized Cost 36,115   36,103      
Gross Unrealized Gains 0   0      
Gross Unrealized Losses (4,395)   (5,414)      
Fair Value 31,720   30,689      
Allowance for Credit Losses 410   425      
Net Carrying Value 35,705   35,678      
Corporate and other debt securities            
Schedule of Held-to-maturity Securities [Line Items]            
Amortized Cost 76,811   81,572      
Gross Unrealized Gains 4   0      
Gross Unrealized Losses (1,234)   (1,541)      
Fair Value 75,581   80,031      
Allowance for Credit Losses 133   173      
Net Carrying Value $ 76,678   $ 81,399