Quarterly report pursuant to Section 13 or 15(d)

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

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SECURITIES (Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Values of Investment Securities) (Details) - USD ($)
$ in Thousands
Mar. 31, 2022
Dec. 31, 2021
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities $ 3,399,980 $ 3,448,784
Gross Unrealized Gains 12,523 65,198
Gross Unrealized (Losses) (219,223) (32,332)
Total AFS securities, Estimated Fair Value 3,193,280 3,481,650
U.S. government and agency securities    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 72,068 73,830
Gross Unrealized Gains   179
Gross Unrealized (Losses) (4,029) (160)
Total AFS securities, Estimated Fair Value 68,039 73,849
Obligations of states and political subdivisions    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 967,219 971,126
Gross Unrealized Gains 8,336 39,343
Gross Unrealized (Losses) (87,255) (2,073)
Total AFS securities, Estimated Fair Value 888,300 1,008,396
Corporate and other bonds    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 185,884 150,201
Gross Unrealized Gains 802 3,353
Gross Unrealized (Losses) (2,763) (178)
Total AFS securities, Estimated Fair Value 183,923 153,376
Commercial    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 451,428 468,893
Gross Unrealized Gains 978 6,900
Gross Unrealized (Losses) (17,915) (4,636)
Total AFS securities, Estimated Fair Value 434,491 471,157
Commercial | Agency    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 342,966 361,806
Gross Unrealized Gains 978 6,761
Gross Unrealized (Losses) (15,592) (4,215)
Total AFS securities, Estimated Fair Value 328,352 364,352
Commercial | Non-agency    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 108,462 107,087
Gross Unrealized Gains   139
Gross Unrealized (Losses) (2,323) (421)
Total AFS securities, Estimated Fair Value 106,139 106,805
Residential    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 1,721,736 1,783,094
Gross Unrealized Gains 2,407 15,423
Gross Unrealized (Losses) (107,261) (25,285)
Total AFS securities, Estimated Fair Value 1,616,882 1,773,232
Residential | Agency    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 1,634,860 1,691,651
Gross Unrealized Gains 2,401 15,180
Gross Unrealized (Losses) (103,848) (24,337)
Total AFS securities, Estimated Fair Value 1,533,413 1,682,494
Residential | Non-agency    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 86,876 91,443
Gross Unrealized Gains 6 243
Gross Unrealized (Losses) (3,413) (948)
Total AFS securities, Estimated Fair Value 83,469 90,738
Other securities    
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]    
Total AFS securities 1,645 1,640
Gross Unrealized Gains 0 0
Gross Unrealized (Losses) 0 0
Total AFS securities, Estimated Fair Value $ 1,645 $ 1,640