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

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).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

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- Definition

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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

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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).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

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