LOANS AND CREDIT QUALITY - Activity in Allowance for Credit Losses by Loan Portfolio (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Allowance for credit losses by loan portfolio
Beginning balance	$ 40,500	$ 41,500	$ 41,500
Charge-offs	(1,105)	(683)	(1,381)
Recoveries	40	94
Provision	242	589
Ending balance	39,677	41,500	40,500
Commercial and industrial loans \| Real Estate Sector
Allowance for credit losses by loan portfolio
Beginning balance	27,912	27,859	27,859
Charge-offs	0	0
Recoveries	0	0
Provision	988	(179)
Ending balance	28,900	27,680	27,912
Commercial and industrial loans \| Commercial and Industrial Sector
Allowance for credit losses by loan portfolio
Beginning balance	3,849	4,277	4,277
Charge-offs	(1,081)	(633)
Recoveries	1	24
Provision	713	658
Ending balance	3,482	4,326	3,849
Commercial and industrial loans \| Non-owner occupied CRE
Allowance for credit losses by loan portfolio
Beginning balance	2,610	2,102	2,102
Charge-offs	0	0
Recoveries	0	0
Provision	(479)	506
Ending balance	2,131	2,608	2,610
Commercial and industrial loans \| Multifamily
Allowance for credit losses by loan portfolio
Beginning balance	13,093	10,974	10,974
Charge-offs	0	0
Recoveries	0	0
Provision	5,854	(1,187)
Ending balance	18,947	9,787	13,093
Commercial and industrial loans \| Multifamily construction
Allowance for credit losses by loan portfolio
Beginning balance	3,983	998	998
Charge-offs	0	0
Recoveries	0	0
Provision	(2,362)	347
Ending balance	1,621	1,345	3,983
Commercial and industrial loans \| CRE construction
Allowance for credit losses by loan portfolio
Beginning balance	189	196	196
Charge-offs	0	0
Recoveries	0	0
Provision	(1)	8
Ending balance	188	204	189
Commercial and industrial loans \| Single family construction
Allowance for credit losses by loan portfolio
Beginning balance	7,365	12,418	12,418
Charge-offs	0	0
Recoveries	0	0
Provision	(1,787)	107
Ending balance	5,578	12,525	7,365
Commercial and industrial loans \| Single family construction to permanent
Allowance for credit losses by loan portfolio
Beginning balance	672	1,171	1,171
Charge-offs	0	0
Recoveries	0	0
Provision	(237)	40
Ending balance	435	1,211	672
Commercial and industrial loans \| Owner occupied CRE
Allowance for credit losses by loan portfolio
Beginning balance	899	1,030	1,030
Charge-offs	0	0
Recoveries	0	0
Provision	(63)	(120)
Ending balance	836	910	899
Commercial and industrial loans \| Commercial business
Allowance for credit losses by loan portfolio
Beginning balance	2,950	3,247	3,247
Charge-offs	(1,081)	(633)	(1,062)
Recoveries	1	24
Provision	776	778
Ending balance	2,646	3,416	2,950
Consumer loans
Allowance for credit losses by loan portfolio
Beginning balance	8,739	9,364	9,364
Charge-offs	(24)	(50)
Recoveries	39	70
Provision	(1,459)	110
Ending balance	7,295	9,494	8,739
Consumer loans \| Single family
Allowance for credit losses by loan portfolio
Beginning balance	5,287	5,610	5,610
Charge-offs	0	0
Recoveries	2	15
Provision	(1,016)	179
Ending balance	4,273	5,804	5,287
Consumer loans \| Home equity and other
Allowance for credit losses by loan portfolio
Beginning balance	3,452	3,754	3,754
Charge-offs	(24)	(50)	(319)
Recoveries	37	55
Provision	(443)	(69)
Ending balance	$ 3,022	$ 3,690	$ 3,452

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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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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- Definition

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 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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