SECURITIES (Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Values of Investment Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	$ 3,225,031	$ 3,448,784
Gross Unrealized Gains	159	65,198
Gross Unrealized (Losses)	(507,867)	(32,332)
Total AFS securities, Estimated Fair Value	2,717,323	3,481,650
U.S. government and agency securities
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	70,399	73,830
Gross Unrealized Gains	0	179
Gross Unrealized (Losses)	(8,763)	(160)
Total AFS securities, Estimated Fair Value	61,636	73,849
Obligations of states and political subdivisions
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	961,722	971,126
Gross Unrealized Gains	7	39,343
Gross Unrealized (Losses)	(197,186)	(2,073)
Total AFS securities, Estimated Fair Value	764,543	1,008,396
Corporate and other bonds
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	246,411	150,201
Gross Unrealized Gains	0	3,353
Gross Unrealized (Losses)	(15,323)	(178)
Total AFS securities, Estimated Fair Value	231,088	153,376
Commercial
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	349,314	468,893
Gross Unrealized Gains	84	6,900
Gross Unrealized (Losses)	(40,824)	(4,636)
Total AFS securities, Estimated Fair Value	308,574	471,157
Commercial \| Agency
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	247,854	361,806
Gross Unrealized Gains	84	6,761
Gross Unrealized (Losses)	(36,739)	(4,215)
Total AFS securities, Estimated Fair Value	211,199	364,352
Commercial \| Non-agency
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	101,460	107,087
Gross Unrealized Gains	0	139
Gross Unrealized (Losses)	(4,085)	(421)
Total AFS securities, Estimated Fair Value	97,375	106,805
Residential
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	1,595,531	1,783,094
Gross Unrealized Gains	68	15,423
Gross Unrealized (Losses)	(245,771)	(25,285)
Total AFS securities, Estimated Fair Value	1,349,828	1,773,232
Residential \| Agency
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	1,520,401	1,691,651
Gross Unrealized Gains	68	15,180
Gross Unrealized (Losses)	(238,966)	(24,337)
Total AFS securities, Estimated Fair Value	1,281,503	1,682,494
Residential \| Non-agency
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	75,130	91,443
Gross Unrealized Gains	0	243
Gross Unrealized (Losses)	(6,805)	(948)
Total AFS securities, Estimated Fair Value	68,325	90,738
Other securities
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	1,654	1,640
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	0	0
Total AFS securities, Estimated Fair Value	$ 1,654	$ 1,640

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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-Subparagraph (b)
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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost excluding accrued interest, before allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Publisher FASB
-Name Accounting Standards Codification
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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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