CREDIT QUALITY ASSESSMENT - Allowance for Credit or Loan Losses by Respective Loan Portfolio Segment (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 136,242	$ 109,145	$ 109,145
Provision/ (credit) for credit losses - loans	(14,491)	4,681	26,680
Charge-offs	(2,265)	(762)	(1,105)
Recoveries	801	606	1,522
Net (charge-offs)/ recoveries	(1,464)	(156)	417
Balance at period end	120,287	113,670	136,242
Total loans	$ 11,369,639		$ 11,396,706
Allowance for credit losses on loans to total loans ratio	1.06%		1.20%
Average loans	$ 11,397,815		$ 10,638,882
Annualized net charge-offs/ (recoveries) to average loans	0.03%		0.00%
Balance of loans individually evaluated for credit loss	$ 63,530		$ 26,197
Allowance related to loans evaluated individually	$ 16,224		$ 6,902
Individual allowance to loans evaluated individually ratio	25.54%		26.35%
Contractual balance of individually evaluated loans	$ 65,687		$ 29,475
Balance of loans collectively evaluated for credit loss	11,306,109		11,370,509
Allowance related to loans evaluated collectively	$ 104,063		$ 129,340
Collective allowance to loans evaluated collectively ratio	0.92%		1.14%
Commercial investor real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Charge-offs	$ 0		$ 0
Total loans	5,131,210		5,130,094
Commercial owner-occupied real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Charge-offs	0		0
Total loans	1,770,135		1,775,037
Commercial AD&C
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Charge-offs	0		0
Total loans	1,045,742		1,090,028
Residential mortgage
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Charge-offs	(160)		(155)
Total loans	1,385,743		1,287,933
Residential construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Charge-offs	0		0
Total loans	190,690		224,772
Commercial real estate: | Commercial investor real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	64,737	45,289	45,289
Provision/ (credit) for credit losses - loans	(3,669)		19,128
Charge-offs	0		0
Recoveries	19		320
Net (charge-offs)/ recoveries	19		320
Balance at period end	61,087		64,737
Total loans	$ 5,131,210		$ 5,130,094
Allowance for credit losses on loans to total loans ratio	1.19%		1.26%
Average loans	$ 5,141,447		$ 4,681,607
Annualized net charge-offs/ (recoveries) to average loans	0.00%		(0.01%)
Balance of loans individually evaluated for credit loss	$ 48,721		$ 9,943
Allowance related to loans evaluated individually	$ 7,908		$ 134
Individual allowance to loans evaluated individually ratio	16.23%		1.35%
Contractual balance of individually evaluated loans	$ 48,886		$ 10,882
Balance of loans collectively evaluated for credit loss	5,082,489		5,120,151
Allowance related to loans evaluated collectively	$ 53,179		$ 64,603
Collective allowance to loans evaluated collectively ratio	1.05%		1.26%
Commercial real estate: | Commercial owner-occupied real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 11,646	11,687	$ 11,687
Provision/ (credit) for credit losses - loans	(2,469)		(90)
Charge-offs	0		0
Recoveries	53		49
Net (charge-offs)/ recoveries	53		49
Balance at period end	9,230		11,646
Total loans	$ 1,770,135		$ 1,775,037
Allowance for credit losses on loans to total loans ratio	0.52%		0.66%
Average loans	$ 1,771,369		$ 1,730,293
Annualized net charge-offs/ (recoveries) to average loans	(0.01%)		0.00%
Balance of loans individually evaluated for credit loss	$ 4,846		$ 6,155
Allowance related to loans evaluated individually	$ 1,226		$ 1,261
Individual allowance to loans evaluated individually ratio	25.30%		20.49%
Contractual balance of individually evaluated loans	$ 5,675		$ 6,849
Balance of loans collectively evaluated for credit loss	1,765,289		1,768,882
Allowance related to loans evaluated collectively	$ 8,004		$ 10,385
Collective allowance to loans evaluated collectively ratio	0.45%		0.59%
Commercial real estate: | Commercial AD&C
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 18,646	20,322	$ 20,322
Provision/ (credit) for credit losses - loans	(8,446)		(1,676)
Charge-offs	0		0
Recoveries	0		0
Net (charge-offs)/ recoveries	0		0
Balance at period end	10,200		18,646
Total loans	$ 1,045,742		$ 1,090,028
Allowance for credit losses on loans to total loans ratio	0.98%		1.71%
Average loans	$ 1,069,927		$ 1,112,936
Annualized net charge-offs/ (recoveries) to average loans	0.00%		0.00%
Balance of loans individually evaluated for credit loss	$ 570		$ 0
Allowance related to loans evaluated individually	$ 102		$ 0
Individual allowance to loans evaluated individually ratio	17.89%		0.00%
Contractual balance of individually evaluated loans	$ 581		$ 0
Balance of loans collectively evaluated for credit loss	1,045,172		1,090,028
Allowance related to loans evaluated collectively	$ 10,098		$ 18,646
Collective allowance to loans evaluated collectively ratio	0.97%		1.71%
Commercial Business
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Total loans	$ 9,370,701		$ 9,451,044
Commercial Business | Commercial business
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	28,027	23,170	23,170
Provision/ (credit) for credit losses - loans	123		4,774
Charge-offs	(423)		(716)
Recoveries	187		799
Net (charge-offs)/ recoveries	(236)		83
Balance at period end	27,914		28,027
Total loans	$ 1,423,614		$ 1,455,885
Allowance for credit losses on loans to total loans ratio	1.96%		1.93%
Average loans	$ 1,443,030		$ 1,351,906
Annualized net charge-offs/ (recoveries) to average loans	0.03%		(0.01%)
Balance of loans individually evaluated for credit loss	$ 9,393		$ 8,274
Allowance related to loans evaluated individually	$ 6,988		$ 5,507
Individual allowance to loans evaluated individually ratio	74.40%		66.56%
Contractual balance of individually evaluated loans	$ 10,545		$ 9,893
Balance of loans collectively evaluated for credit loss	1,414,221		1,447,611
Allowance related to loans evaluated collectively	$ 20,926		$ 22,520
Collective allowance to loans evaluated collectively ratio	1.48%		1.56%
Residential real estate: | Residential mortgage
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 9,424	5,384	$ 5,384
Provision/ (credit) for credit losses - loans	(207)		4,093
Charge-offs	(160)		(155)
Recoveries	104		102
Net (charge-offs)/ recoveries	(56)		(53)
Balance at period end	9,161		9,424
Total loans	$ 1,385,743		$ 1,287,933
Allowance for credit losses on loans to total loans ratio	0.66%		0.73%
Average loans	$ 1,330,912		$ 1,117,053
Annualized net charge-offs/ (recoveries) to average loans	0.01%		0.00%
Balance of loans individually evaluated for credit loss	$ 0		$ 1,487
Allowance related to loans evaluated individually	$ 0		$ 0
Individual allowance to loans evaluated individually ratio	0.00%		0.00%
Contractual balance of individually evaluated loans	$ 0		$ 1,487
Balance of loans collectively evaluated for credit loss	1,385,743		1,286,446
Allowance related to loans evaluated collectively	$ 9,161		$ 9,424
Collective allowance to loans evaluated collectively ratio	0.66%		0.73%
Residential real estate: | Residential construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 1,337	1,048	$ 1,048
Provision/ (credit) for credit losses - loans	(487)		281
Charge-offs	0		0
Recoveries	0		8
Net (charge-offs)/ recoveries	0		8
Balance at period end	850		1,337
Total loans	$ 190,690		$ 224,772
Allowance for credit losses on loans to total loans ratio	0.45%		0.59%
Average loans	$ 217,419		$ 221,341
Annualized net charge-offs/ (recoveries) to average loans	0.00%		0.00%
Balance of loans individually evaluated for credit loss	$ 0		$ 0
Allowance related to loans evaluated individually	$ 0		$ 0
Individual allowance to loans evaluated individually ratio	0.00%		0.00%
Contractual balance of individually evaluated loans	$ 0		$ 0
Balance of loans collectively evaluated for credit loss	190,690		224,772
Allowance related to loans evaluated collectively	$ 850		$ 1,337
Collective allowance to loans evaluated collectively ratio	0.45%		0.59%
Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 2,425	$ 2,245	$ 2,245
Provision/ (credit) for credit losses - loans	664		170
Charge-offs	(1,682)		(234)
Recoveries	438		244
Net (charge-offs)/ recoveries	(1,244)		10
Balance at period end	1,845		2,425
Total loans	$ 422,505		$ 432,957
Allowance for credit losses on loans to total loans ratio	0.44%		0.56%
Average loans	$ 423,711		$ 423,746
Annualized net charge-offs/ (recoveries) to average loans	0.59%		0.00%
Balance of loans individually evaluated for credit loss	$ 0		$ 338
Allowance related to loans evaluated individually	$ 0		$ 0
Individual allowance to loans evaluated individually ratio	0.00%		0.00%
Contractual balance of individually evaluated loans	$ 0		$ 364
Balance of loans collectively evaluated for credit loss	422,505		432,619
Allowance related to loans evaluated collectively	$ 1,845		$ 2,425
Collective allowance to loans evaluated collectively ratio	0.44%		0.56%