v3.26.3
INVESTMENT SECURITIES - Schedule of Amortized Cost and Estimated Fair Value of Available-for-Sale and Held-to-Maturity Investment Securities (Details) - USD ($)
Sep. 30, 2026
Jun. 30, 2026
Dec. 31, 2025
Sep. 30, 2025
Jun. 30, 2025
Dec. 31, 2024
Investments, Debt and Equity Securities [Abstract]            
Trading securities $ 0          
Available-for-Sale Debt Securities            
Amortized Cost 4,373,381,000   $ 4,037,700,000      
Gross Unrealized Gain 1,000   2,832,000      
Gross Unrealized Loss 682,265,000   498,286,000      
Allowance for Credit Losses 0   0      
Fair Value 3,691,117,000   3,542,246,000      
Held-to-Maturity Debt Securities            
Amortized Cost 925,727,000   968,336,000      
Gross Unrealized Gain 0   1,157,000      
Gross Unrealized Loss 155,243,000   90,422,000      
Beginning balance 5,000 $ 5,000 5,000 $ 6,000 $ 6,000 $ 7,000
Fair Value 770,479,000   879,066,000      
Available for sale securities transfers to held to maturity unrealized losses 71,900,000   83,400,000      
Collateralized mortgage obligations (CMO)            
Available-for-Sale Debt Securities            
Amortized Cost 468,498,000   476,409,000      
Gross Unrealized Gain 0   416,000      
Gross Unrealized Loss 86,683,000   71,679,000      
Allowance for Credit Losses 0   0      
Fair Value 381,815,000   405,146,000      
Fannie Mae (FNMA) mortgage-backed securities (MBS)            
Available-for-Sale Debt Securities            
Amortized Cost 3,442,307,000   3,167,210,000      
Gross Unrealized Gain 1,000   2,289,000      
Gross Unrealized Loss 533,641,000   384,092,000      
Allowance for Credit Losses 0   0      
Fair Value 2,908,667,000   2,785,407,000      
Held-to-Maturity Debt Securities            
Amortized Cost 752,574,000   788,439,000      
Gross Unrealized Gain 0   0      
Gross Unrealized Loss 144,015,000   89,936,000      
Beginning balance 0   0      
Fair Value 608,559,000   698,503,000      
Freddie Mac (FHLMC) MBS            
Available-for-Sale Debt Securities            
Amortized Cost 155,550,000   123,979,000      
Gross Unrealized Gain 0   68,000      
Gross Unrealized Loss 14,028,000   7,542,000      
Allowance for Credit Losses 0   0      
Fair Value 141,522,000   116,505,000      
Ginnie Mae (GNMA) MBS            
Available-for-Sale Debt Securities            
Amortized Cost 88,656,000   49,804,000      
Gross Unrealized Gain 0   59,000      
Gross Unrealized Loss 7,525,000   2,480,000      
Allowance for Credit Losses 0   0      
Fair Value 81,131,000   47,383,000      
Government-sponsored enterprises (GSE) agency notes            
Available-for-Sale Debt Securities            
Amortized Cost 218,370,000   220,298,000      
Gross Unrealized Gain 0   0      
Gross Unrealized Loss 40,388,000   32,493,000      
Allowance for Credit Losses 0   0      
Fair Value 177,982,000   187,805,000      
State and political subdivisions            
Held-to-Maturity Debt Securities            
Amortized Cost 173,153,000   179,897,000      
Gross Unrealized Gain 0   1,157,000      
Gross Unrealized Loss 11,228,000   486,000      
Beginning balance 5,000   5,000      
Fair Value $ 161,920,000   $ 180,563,000