Quarterly report [Sections 13 or 15(d)]

SECURITIES AND OTHER INVESTMENTS (Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Values of Investment Securities) (Details)

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SECURITIES AND OTHER INVESTMENTS (Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Values of Investment Securities) (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities $ 4,333,481 $ 4,489,998
Gross Unrealized Gains 11,057 19,804
Gross Unrealized (Losses) (333,128) (315,501)
Total AFS securities, Estimated Fair Value 4,011,410 4,194,301
US Government Agencies Debt Securities [Member]    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 101,788 103,335
Gross Unrealized Gains 392 681
Gross Unrealized (Losses) (77) (14)
Total AFS securities, Estimated Fair Value 102,103 104,002
US States and Political Subdivisions Debt Securities [Member]    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 587,355 589,194
Gross Unrealized Gains 118 178
Gross Unrealized (Losses) (115,269) (101,487)
Total AFS securities, Estimated Fair Value 472,204 487,885
Corporate Bond Securities [Member]    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 216,280 221,432
Gross Unrealized Gains 466 709
Gross Unrealized (Losses) (3,736) (4,207)
Total AFS securities, Estimated Fair Value 213,010 217,934
Commercial Mortgage-Backed Securities [Member]    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 459,683 469,414
Gross Unrealized Gains 913 1,463
Gross Unrealized (Losses) (42,407) (41,711)
Total AFS securities, Estimated Fair Value 418,189 429,166
Commercial Mortgage-Backed Securities [Member] | Agency Securities [Member]    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 347,910 354,405
Gross Unrealized Gains 809 1,276
Gross Unrealized (Losses) (40,053) (39,806)
Total AFS securities, Estimated Fair Value 308,666 315,875
Commercial Mortgage-Backed Securities [Member] | Non-agency    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 111,773 115,009
Gross Unrealized Gains 104 187
Gross Unrealized (Losses) (2,354) (1,905)
Total AFS securities, Estimated Fair Value 109,523 113,291
Residential Mortgage-Backed Securities [Member]    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 2,966,395 3,104,667
Gross Unrealized Gains 9,168 16,773
Gross Unrealized (Losses) (171,639) (168,082)
Total AFS securities, Estimated Fair Value 2,803,924 2,953,358
Residential Mortgage-Backed Securities [Member] | Agency Securities [Member]    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 2,808,181 2,942,900
Gross Unrealized Gains 8,408 15,838
Gross Unrealized (Losses) (168,862) (165,524)
Total AFS securities, Estimated Fair Value 2,647,727 2,793,214
Residential Mortgage-Backed Securities [Member] | Non-agency    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 158,214 161,767
Gross Unrealized Gains 760 935
Gross Unrealized (Losses) (2,777) (2,558)
Total AFS securities, Estimated Fair Value 156,197 160,144
Collateralized Securities, Other [Member]    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 1,980 1,956
Gross Unrealized Gains 0 0
Gross Unrealized (Losses) 0 0
Total AFS securities, Estimated Fair Value $ 1,980 $ 1,956