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Investment Securities Schedule of Amortized Cost and Fair Values of Investment Securities (Details) - USD ($)
$ in Thousands
Sep. 30, 2025
Dec. 31, 2024
Schedule of Investments [Line Items]    
Amortized Cost $ 3,847,076  
Gross Unrealized Gains 19,954  
Gross Unrealized Losses (272,954)  
Estimated Fair Value 3,594,076 $ 3,410,899
Amortized Cost, Held to Maturity 1,451,194 1,395,569
Gross Unrealized Gains, Held to Maturity 3,819 2
Gross Unrealized Losses, Held to Maturity (169,663) (212,122)
Debt Securities, Held-to-Maturity, Fair Value 1,285,350 1,183,449
US States and Political Subdivisions Debt Securities [Member]    
Schedule of Investments [Line Items]    
Amortized Cost 954,132 960,227
Gross Unrealized Gains 155 106
Gross Unrealized Losses (142,551) (145,446)
Estimated Fair Value 811,736 814,887
Corporate Debt Securities [Member]    
Schedule of Investments [Line Items]    
Amortized Cost 261,087 313,681
Gross Unrealized Gains 1,125 1,123
Gross Unrealized Losses (7,173) (14,434)
Estimated Fair Value 255,039 300,370
Collateralized Mortgage Obligations [Member]    
Schedule of Investments [Line Items]    
Amortized Cost 1,129,328 798,157
Gross Unrealized Gains 13,744 4,629
Gross Unrealized Losses (7,630) (13,901)
Estimated Fair Value 1,135,442 788,885
Mortgage-Backed Securities [Member]    
Schedule of Investments [Line Items]    
Amortized Cost 877,560 1,029,846
Gross Unrealized Gains 4,923 30
Gross Unrealized Losses (23,491) (40,001)
Estimated Fair Value 858,992 989,875
Amortized Cost, Held to Maturity 597,922 537,856
Gross Unrealized Gains, Held to Maturity 3,819 2
Gross Unrealized Losses, Held to Maturity (45,910) (60,162)
Debt Securities, Held-to-Maturity, Fair Value 555,831 477,696
Commercial Mortgage Backed Securities [Member]    
Schedule of Investments [Line Items]    
Amortized Cost 624,969 617,605
Gross Unrealized Gains 7 0
Gross Unrealized Losses (92,109) (100,723)
Estimated Fair Value 532,867 516,882
Amortized Cost, Held to Maturity 853,272 857,713
Gross Unrealized Gains, Held to Maturity 0 0
Gross Unrealized Losses, Held to Maturity (123,753) (151,960)
Debt Securities, Held-to-Maturity, Fair Value $ 729,519 705,753
Debt Securities [Member]    
Schedule of Investments [Line Items]    
Amortized Cost   3,719,516
Gross Unrealized Gains   5,888
Gross Unrealized Losses   (314,505)
Estimated Fair Value   $ 3,410,899