CREDIT QUALITY ASSESSMENT - Credit Quality of Loan Portfolio, New (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Total loans	$ 11,369,639	$ 11,396,706
Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	11,320,180	11,357,347
Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	48,738	34,782
Loans greater than 90 days past due	721	1,002
Restructured loans	0	3,575
Total loans	49,459	39,359
Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	11,303,348	11,312,130
30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	12,341	32,576
60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	4,491	12,641
Commercial investor real estate
Financing Receivable, Past Due [Line Items]
Total loans	5,131,210	5,130,094
Commercial owner-occupied real estate
Financing Receivable, Past Due [Line Items]
Total loans	1,770,135	1,775,037
Commercial AD&C
Financing Receivable, Past Due [Line Items]
Total loans	1,045,742	1,090,028
Residential mortgage
Financing Receivable, Past Due [Line Items]
Total loans	1,385,743	1,287,933
Residential construction
Financing Receivable, Past Due [Line Items]
Total loans	190,690	224,772
Commercial real estate: | Commercial investor real estate
Financing Receivable, Past Due [Line Items]
Total loans	5,131,210	5,130,094
Commercial real estate: | Commercial investor real estate | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	5,110,829	5,120,151
Commercial real estate: | Commercial investor real estate | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	20,381	9,943
Loans greater than 90 days past due	0	0
Restructured loans	0	0
Total loans	20,381	9,943
Commercial real estate: | Commercial investor real estate | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	5,108,614	5,104,204
Commercial real estate: | Commercial investor real estate | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	2,215	9,735
Commercial real estate: | Commercial investor real estate | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	0	6,212
Commercial real estate: | Commercial owner-occupied real estate
Financing Receivable, Past Due [Line Items]
Total loans	1,770,135	1,775,037
Commercial real estate: | Commercial owner-occupied real estate | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,765,289	1,768,882
Commercial real estate: | Commercial owner-occupied real estate | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	4,846	5,019
Loans greater than 90 days past due	0	0
Restructured loans	0	1,136
Total loans	4,846	6,155
Commercial real estate: | Commercial owner-occupied real estate | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,763,223	1,767,875
Commercial real estate: | Commercial owner-occupied real estate | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	2,066	1,007
Commercial real estate: | Commercial owner-occupied real estate | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	0	0
Commercial real estate: | Commercial AD&C
Financing Receivable, Past Due [Line Items]
Total loans	1,045,742	1,090,028
Commercial real estate: | Commercial AD&C | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,045,173	1,090,028
Commercial real estate: | Commercial AD&C | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	569	0
Loans greater than 90 days past due	0	0
Restructured loans	0	0
Total loans	569	0
Commercial real estate: | Commercial AD&C | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,044,320	1,090,028
Commercial real estate: | Commercial AD&C | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	0	0
Commercial real estate: | Commercial AD&C | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	853	0
Commercial Business
Financing Receivable, Past Due [Line Items]
Total loans	9,370,701	9,451,044
Commercial Business | Commercial business
Financing Receivable, Past Due [Line Items]
Total loans	1,423,614	1,455,885
Commercial Business | Commercial business | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,414,192	1,446,609
Commercial Business | Commercial business | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	9,393	7,322
Loans greater than 90 days past due	29	1,002
Restructured loans	0	952
Total loans	9,422	9,276
Commercial Business | Commercial business | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,413,058	1,443,012
Commercial Business | Commercial business | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	747	3,556
Commercial Business | Commercial business | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	387	41
Residential real estate: | Residential mortgage
Financing Receivable, Past Due [Line Items]
Total loans	1,385,743	1,287,933
Residential real estate: | Residential mortgage | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,374,898	1,279,007
Residential real estate: | Residential mortgage | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	10,153	7,439
Loans greater than 90 days past due	692	0
Restructured loans	0	1,487
Total loans	10,845	8,926
Residential real estate: | Residential mortgage | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,366,644	1,261,878
Residential real estate: | Residential mortgage | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	5,464	11,307
Residential real estate: | Residential mortgage | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	2,790	5,822
Residential real estate: | Residential construction
Financing Receivable, Past Due [Line Items]
Total loans	190,690	224,772
Residential real estate: | Residential construction | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	190,690	224,772
Residential real estate: | Residential construction | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0	0
Loans greater than 90 days past due	0	0
Restructured loans	0	0
Total loans	0	0
Residential real estate: | Residential construction | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	190,690	222,144
Residential real estate: | Residential construction | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	0	2,628
Residential real estate: | Residential construction | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	0	0
Consumer
Financing Receivable, Past Due [Line Items]
Total loans	422,505	432,957
Consumer | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	419,109	427,898
Consumer | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	3,396	5,059
Loans greater than 90 days past due	0	0
Restructured loans	0	0
Total loans	3,396	5,059
Consumer | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	416,799	422,989
Consumer | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,849	4,343
Consumer | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	$ 461	$ 566