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LOANS AND ALLOWANCE FOR CREDIT LOSSES - Loan Summary (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Loans receivable, net
Loans	$ 9,704,598	$ 8,809,394
Allowance for credit losses	(66,669)	(61,059)	$ (50,672)
Loans, net of allowance for credit losses	9,637,929	8,748,335
Net deferred loan origination costs	81,600	73,800
Loans receivable, related parties
Balance at beginning of year	12,373	13,773
New loans	1,372	2,025
Payments	(2,053)	(3,425)
Balance at end of year	11,692	12,373	13,773
CRE - multifamily
Loans receivable, net
Loans	619,794	484,773
CRE - owner occupied
Loans receivable, net
Loans	752,774	722,387
CRE - non-owner occupied
Loans receivable, net
Loans	1,711,198	1,431,720
Commercial & industrial and other business loans
Loans receivable, net
Loans	1,000,630	1,006,785
Business lending
Loans receivable, net
Loans	4,084,396	3,645,665
Consumer mortgage
Loans receivable, net
Loans	3,285,018	3,012,475
Consumer indirect
Loans receivable, net
Loans	1,703,440	1,539,653
Consumer direct
Loans receivable, net
Loans	185,229	177,605
Home equity
Loans receivable, net
Loans	446,515	433,996
Unallocated
Loans receivable, net
Allowance for credit losses			(1,000)
Commercial Portfolio Segment
Loans receivable, net
Allowance for credit losses				$ (62,358)
Commercial Portfolio Segment \| CRE - multifamily
Loans receivable, net
Loans	619,794	484,773
Commercial Portfolio Segment \| CRE - owner occupied
Loans receivable, net
Loans	752,774	722,387
Commercial Portfolio Segment \| CRE - non-owner occupied
Loans receivable, net
Loans	1,711,198	1,431,720
Commercial Portfolio Segment \| Commercial & industrial and other business loans
Loans receivable, net
Loans	1,000,630	1,006,785
Commercial Portfolio Segment \| Business lending
Loans receivable, net
Allowance for credit losses		(23,297)	(22,995)	(30,072)
Commercial Portfolio Segment \| Unallocated
Loans receivable, net
Allowance for credit losses				(1,000)
Residential Portfolio Segment \| Consumer mortgage
Loans receivable, net
Loans	3,285,018	3,012,475
Allowance for credit losses	(15,333)	(14,343)	(10,017)	(10,672)
Residential Portfolio Segment \| Home equity
Loans receivable, net
Allowance for credit losses	(1,628)	(1,594)	(1,814)	(2,222)
Consumer Portfolio Segment \| Business lending
Loans receivable, net
Allowance for credit losses	(26,854)	(23,297)
Consumer Portfolio Segment \| Consumer indirect
Loans receivable, net
Loans	1,703,440	1,539,653
Allowance for credit losses	(18,585)	(17,852)	(11,737)	(13,696)
Consumer Portfolio Segment \| Consumer direct
Loans receivable, net
Loans	185,229	177,605
Allowance for credit losses	(3,269)	(2,973)	(2,306)	$ (3,207)
Consumer Portfolio Segment \| Home equity
Loans receivable, net
Loans	446,515	433,996
Total Allowances For Credit Losses
Loans receivable, net
Allowance for credit losses	$ (67,582)	$ (62,182)	$ (50,672)