v3.26.3
Investment Securities (Tables)
 9 Months Ended
Sep. 30, 2026
Investments, Debt and Equity Securities [Abstract]  
Summary of Amortized Cost and Estimated Fair Values of Available for Sale Securities
Securities held for indefinite periods of time are classified as available for sale and carried at estimated fair value. The amortized cost and estimated fair values of securities available for sale are summarized as follows.
 
     September 30, 2026  
            Gross      Gross      Allowance      Estimated  
     Amortized      Unrealized      Unrealized      For Credit      Fair  
     Cost      Gains      Losses      Losses      Value  
U.S. Treasury securities and obligations of U.S. Government corporations and agencies
    $ 273,233      $ 17      $ 1,501      $ 0      $ 271,749  
State and political subdivisions
      562,533        6        85,935        0        476,604  
Residential mortgage-backed securities
               
Agency
      2,284,302        5        194,960        0        2,089,347  
Non-agency
      32,912        153        5,236        0        27,829  
Commercial mortgage-backed securities
               
Agency
      324,215        32        23,394        0        300,853  
Asset-backed securities
      151,445        38        1,887        0        149,596  
Single issue trust preferred securities
      13,337        0        353        0        12,984  
Other corporate securities
      180,268        0        8,735        0        171,533  
  
 
 
     
 
 
     
 
 
     
 
 
     
 
 
  
Total
    $ 3,822,245      $ 251      $ 322,001      $ 0      $ 3,500,495  
  
 
 
     
 
 
     
 
 
     
 
 
     
 
 
  
 
     December 31, 2025  
            Gross      Gross      Allowance      Estimated  
     Amortized      Unrealized      Unrealized      For Credit      Fair  
     Cost      Gains      Losses      Losses      Value  
U.S. Treasury securities and obligations of U.S. Government corporations and agencies
    $ 283,058      $ 75      $ 1,476      $ 0      $ 281,657  
State and political subdivisions
      572,217        343        55,634        0        516,926  
Residential mortgage-backed securities
               
Agency
      1,467,436        5,517        114,317        0        1,358,636  
Non-agency
      42,792        330        4,237        0        38,885  
Commercial mortgage-backed securities
               
Agency
      416,177        4,948        26,052        0        395,073  
Asset-backed securities
      225,617        18        2,381        0        223,254  
Single issue trust preferred securities
      13,319        0        661        0        12,658  
Other corporate securities
      244,244        0        11,881        0        232,363  
  
 
 
     
 
 
     
 
 
     
 
 
     
 
 
  
Total
    $ 3,264,860      $ 11,231      $ 216,639      $ 0      $ 3,059,452  
  
 
 
     
 
 
     
 
 
     
 
 
     
 
 
  
Summary of Securities Available for Sale in an Unrealized Loss Position
The following is a summary of securities available for sale which were in an unrealized loss position at September 30, 2026 and December 31, 2025.
 
     Less than 12 months      12 months or longer      Total  
     Fair      Unrealized      Fair      Unrealized      Fair      Unrealized  
     Value      Losses      Value      Losses      Value      Losses  
September 30, 2026
                  
U.S. Treasury securities and obligations of U.S. Government corporations and agencies
    $ 507      $ 6      $ 22,051      $ 1,495      $ 22,558      $ 1,501  
State and political subdivisions
      23,535        2,237        444,364        83,698        467,899        85,935  
Residential mortgage-backed securities
                  
Agency
      1,373,378        53,079        675,737        141,881        2,049,115        194,960  
Non-agency
      0        0        19,865        5,236        19,865        5,236  
Commercial mortgage-backed securities
                  
Agency
      84,294        1,862        212,641        21,532        296,935        23,394  
Asset-backed securities
      2,065        15        126,898        1,872        128,963        1,887  
Single issue trust preferred securities
      0        0        12,984        353        12,984        353  
Other corporate securities
      5,946        51        161,176        8,684        167,122        8,735  
  
 
 
     
 
 
     
 
 
     
 
 
     
 
 
     
 
 
  
Total
    $ 1,489,725      $ 57,250      $ 1,675,716      $ 264,751      $ 3,165,441      $ 322,001  
  
 
 
     
 
 
     
 
 
     
 
 
     
 
 
     
 
 
  
 
     Less than 12 months      12 months or longer      Total  
     Fair      Unrealized      Fair      Unrealized      Fair      Unrealized  
     Value      Losses      Value      Losses      Value      Losses  
December 31, 2025
                  
U.S. Treasury securities and obligations of U.S. Government corporations and agencies
    $ 133      $ 1      $ 31,485      $ 1,475      $ 31,618      $ 1,476  
State and political subdivisions
      6,177        543        483,564        55,091        489,741        55,634  
Residential mortgage-backed securities
                  
Agency
      109,848        270        795,183        114,047        905,031        114,317  
Non-agency
      0        0        21,189        4,237        21,189        4,237  
Commercial mortgage-backed securities
                  
Agency
      6,287        4        293,038        26,048        299,325        26,052  
Asset-backed securities
      50,181        154        136,940        2,227        187,121        2,381  
Single issue trust preferred securities
      0        0        12,658        661        12,658        661  
Other corporate securities
      0        0        224,942        11,881        224,942        11,881  
  
 
 
     
 
 
     
 
 
     
 
 
     
 
 
     
 
 
  
Total
    $ 172,626      $ 972      $ 1,998,999      $ 215,667      $ 2,171,625      $ 216,639  
  
 
 
     
 
 
     
 
 
     
 
 
     
 
 
     
 
 
  
Summary of Gains or Losses on Proceeds from Maturities, Sales and Calls of Available for Sale Securities by Specific Identification Method
The following table shows the proceeds from maturities, sales and calls of available for sale securities and the gross realized gains and losses on sales and calls of those securities that have been included in earnings as a result of any sales and calls. Gains or losses on sales and calls of available for sale securities were recognized by the specific identification method.
 
    
Three Months Ended

September 30
     
Nine Months Ended

September 30
  
    
2026
     
2025
     
2026
     
2025
  
Proceeds from sales, calls and maturities
    $ 389,858      $ 663,951      $ 1,187,431      $ 1,582,013  
Gross realized gains
      0        0        0        0  
Gross realized losses
      0        0        9,728        0  
Summary of Maturities of Debt Securities Held to Maturity by Amortized Cost and Estimated Fair Value
     September 30, 2026      December 31, 2025  
            Estimated             Estimated  
     Amortized      Fair      Amortized      Fair  
     Cost      Value      Cost      Value  
Due in one year or less
    $ 292,924      $ 292,540      $ 298,573      $ 298,193  
Due after one year through five years
      518,718        478,794        527,383        494,204  
Due after five years through ten years
      514,207        464,232        559,647        521,011  
Due after ten years
      2,496,396        2,264,929        1,879,257        1,746,044  
  
 
 
     
 
 
     
 
 
     
 
 
  
Total
    $ 3,822,245      $ 3,500,495      $ 3,264,860      $ 3,059,452  
  
 
 
     
 
 
     
 
 
     
 
 
  
Summary of Equity Securities
     Three Months Ended
September 30		      Nine Months Ended
September 30		  
     2026      2025      2026      2025  
Net gains recognized during the period on equity securities sold
    $ 59      $ 0      $ 4,170      $ 0  
Unrealized gains recognized during the period on equity securities still held at period end
      138        10,442        5,005        11,421  
Unrealized losses recognized during the period on equity securities still held at period end
      (545 )       0        (601 )       (33 ) 
  
 
 
     
 
 
     
 
 
     
 
 
  
Net (losses) gains recognized during the period
    $ (348 )     $ 10,442      $ 8,574      $ 11,388