v3.26.1
INVESTMENT SECURITIES - Schedule of Amortized Cost and Estimated Fair Value of Available-for-Sale and Held-to-Maturity Investment Securities (Details) - USD ($)
Jun. 30, 2026
Mar. 31, 2026
Dec. 31, 2025
Jun. 30, 2025
Mar. 31, 2025
Dec. 31, 2024
Investments, Debt and Equity Securities [Abstract]            
Trading securities $ 0          
Available-for-Sale Debt Securities            
Amortized Cost 4,359,331,000   $ 4,037,700,000      
Gross Unrealized Gain 1,786,000   2,832,000      
Gross Unrealized Loss 520,109,000   498,286,000      
Allowance for Credit Losses 0   0      
Fair Value 3,841,008,000   3,542,246,000      
Held-to-Maturity Debt Securities            
Amortized Cost 943,297,000   968,336,000      
Gross Unrealized Gain 580,000   1,157,000      
Gross Unrealized Loss 98,041,000   90,422,000      
Beginning balance 5,000 $ 5,000 5,000 $ 6,000 $ 6,000 $ 7,000
Fair Value 845,831,000   879,066,000      
Available for sale securities transfers to held to maturity unrealized losses (75,800,000)   (83,400,000)      
Collateralized mortgage obligations (CMO)            
Available-for-Sale Debt Securities            
Amortized Cost 455,189,000   476,409,000      
Gross Unrealized Gain 237,000   416,000      
Gross Unrealized Loss 73,447,000   71,679,000      
Allowance for Credit Losses 0   0      
Fair Value 381,979,000   405,146,000      
Fannie Mae (FNMA) mortgage-backed securities (MBS)            
Available-for-Sale Debt Securities            
Amortized Cost 3,436,640,000   3,167,210,000      
Gross Unrealized Gain 1,288,000   2,289,000      
Gross Unrealized Loss 401,338,000   384,092,000      
Allowance for Credit Losses 0   0      
Fair Value 3,036,590,000   2,785,407,000      
Held-to-Maturity Debt Securities            
Amortized Cost 766,440,000   788,439,000      
Gross Unrealized Gain 0   0      
Gross Unrealized Loss 97,327,000   89,936,000      
Beginning balance 0   0      
Fair Value 669,113,000   698,503,000      
Freddie Mac (FHLMC) MBS            
Available-for-Sale Debt Securities            
Amortized Cost 157,384,000   123,979,000      
Gross Unrealized Gain 34,000   68,000      
Gross Unrealized Loss 8,683,000   7,542,000      
Allowance for Credit Losses 0   0      
Fair Value 148,735,000   116,505,000      
Ginnie Mae (GNMA) MBS            
Available-for-Sale Debt Securities            
Amortized Cost 91,106,000   49,804,000      
Gross Unrealized Gain 227,000   59,000      
Gross Unrealized Loss 2,917,000   2,480,000      
Allowance for Credit Losses 0   0      
Fair Value 88,416,000   47,383,000      
Government-sponsored enterprises (GSE) agency notes            
Available-for-Sale Debt Securities            
Amortized Cost 219,012,000   220,298,000      
Gross Unrealized Gain 0   0      
Gross Unrealized Loss 33,724,000   32,493,000      
Allowance for Credit Losses 0   0      
Fair Value 185,288,000   187,805,000      
State and political subdivisions            
Held-to-Maturity Debt Securities            
Amortized Cost 176,857,000   179,897,000      
Gross Unrealized Gain 580,000   1,157,000      
Gross Unrealized Loss 714,000   486,000      
Beginning balance 5,000   5,000      
Fair Value $ 176,718,000   $ 180,563,000