ALLOWANCE FOR CREDIT LOSSES AND CREDIT QUALITY - Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 71,972	$ 72,606	$ 72,606
Provision for credit losses	1,520	4,350
Loans charged-off	(504)	(5,896)	(7,332)
Recoveries	192	155
Net loans (charged-off) recovered	(312)	(5,741)
Ending balance	73,180	71,215	71,972
Unallocated
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	372	554	554
Provision for credit losses	129	286
Loans charged-off	0	0
Recoveries	0	0
Net loans (charged-off) recovered	0	0
Ending balance	501	840	372
Commercial Portfolio Segment \| Commercial and Industrial
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	30,338	35,290	35,290
Provision for credit losses	542	1,504
Loans charged-off	(194)	(5,644)
Recoveries	34	40
Net loans (charged-off) recovered	(160)	(5,604)
Ending balance	30,720	31,190	30,338
Commercial Portfolio Segment \| Commercial Real Estate and Multifamily Residential
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	31,335	27,394	27,394
Provision for credit losses	717	1,642
Loans charged-off	0	0
Recoveries	26	0
Net loans (charged-off) recovered	26	0
Ending balance	32,078	29,036	31,335
Commercial Portfolio Segment \| Agri-business and Agricultural
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	4,150	4,429	4,429
Provision for credit losses	(38)	192
Loans charged-off	0	0
Recoveries	0	0
Net loans (charged-off) recovered	0	0
Ending balance	4,112	4,621	4,150
Commercial Portfolio Segment \| Other Commercial
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,129	917	917
Provision for credit losses	(107)	117
Loans charged-off	0	0
Recoveries	0	0
Net loans (charged-off) recovered	0	0
Ending balance	1,022	1,034	1,129
Consumer Portfolio Segment \| Consumer 1-4 Family Mortgage
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,474	3,001	3,001
Provision for credit losses	21	394
Loans charged-off	0	0
Recoveries	23	3
Net loans (charged-off) recovered	23	3
Ending balance	3,518	3,398	3,474
Consumer Portfolio Segment \| Other Consumer
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,174	1,021	1,021
Provision for credit losses	256	215
Loans charged-off	(310)	(252)
Recoveries	109	112
Net loans (charged-off) recovered	(201)	(140)
Ending balance	$ 1,229	$ 1,096	$ 1,174

Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

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- Definition

Amount, excluding accrued interest, of increase in allowance for credit loss on financing receivable from recovery. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

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- Definition

Amount, excluding accrued interest, of decrease (increase) in allowance for credit loss on financing receivable from writeoff (recovery). Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

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- Definition

Amount, excluding accrued interest, of credit loss expense (reversal of expense) on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

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