CREDIT QUALITY ASSESSMENT - Credit Quality of Loan Portfolio, New (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Total loans	$ 10,144,328	$ 9,967,091
Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	10,098,002	9,918,281
Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	43,869	46,086
Loans greater than 90 days past due	296	557
Restructured loans	2,161	2,167
Total non-performing loans	46,326	48,810
Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	10,074,964	9,901,309
30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	14,690	12,475
60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	8,348	4,497
Commercial investor real estate
Financing Receivable, Past Due [Line Items]
Total loans	4,388,275	4,141,346
Commercial owner-occupied real estate
Financing Receivable, Past Due [Line Items]
Total loans	1,692,253	1,690,881
Commercial AD&C
Financing Receivable, Past Due [Line Items]
Total loans	1,089,331	1,088,094
Residential mortgage
Financing Receivable, Past Due [Line Items]
Total loans	1,000,697	937,570
Residential construction
Financing Receivable, Past Due [Line Items]
Total loans	204,259	197,652
Commercial real estate: | Commercial investor real estate
Financing Receivable, Past Due [Line Items]
Total loans	4,388,275	4,141,346
Commercial real estate: | Commercial investor real estate | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	4,376,532	4,128,857
Commercial real estate: | Commercial investor real estate | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	11,743	12,489
Loans greater than 90 days past due	0	0
Restructured loans	0	0
Total non-performing loans	11,743	12,489
Commercial real estate: | Commercial investor real estate | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	4,374,107	4,127,009
Commercial real estate: | Commercial investor real estate | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	2,425	1,656
Commercial real estate: | Commercial investor real estate | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	0	192
Commercial real estate: | Commercial owner-occupied real estate
Financing Receivable, Past Due [Line Items]
Total loans	1,692,253	1,690,881
Commercial real estate: | Commercial owner-occupied real estate | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,684,170	1,681,575
Commercial real estate: | Commercial owner-occupied real estate | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	8,083	9,306
Loans greater than 90 days past due	0	0
Restructured loans	0	0
Total non-performing loans	8,083	9,306
Commercial real estate: | Commercial owner-occupied real estate | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,680,971	1,680,635
Commercial real estate: | Commercial owner-occupied real estate | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	377	86
Commercial real estate: | Commercial owner-occupied real estate | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	2,822	854
Commercial real estate: | Commercial AD&C
Financing Receivable, Past Due [Line Items]
Total loans	1,089,331	1,088,094
Commercial real estate: | Commercial AD&C | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,088,250	1,087,444
Commercial real estate: | Commercial AD&C | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	1,081	650
Loans greater than 90 days past due	0	0
Restructured loans	0	0
Total non-performing loans	1,081	650
Commercial real estate: | Commercial AD&C | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,081,248	1,085,642
Commercial real estate: | Commercial AD&C | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	3,236	1,802
Commercial real estate: | Commercial AD&C | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	3,766	0
Commercial Business
Financing Receivable, Past Due [Line Items]
Total loans	8,519,461	8,402,155
Commercial Business | Commercial business
Financing Receivable, Past Due [Line Items]
Total loans	1,349,602	1,481,834
Commercial Business | Commercial business | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,340,620	1,472,801
Commercial Business | Commercial business | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	8,357	8,420
Loans greater than 90 days past due	0	0
Restructured loans	625	613
Total non-performing loans	8,982	9,033
Commercial Business | Commercial business | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,339,424	1,471,669
Commercial Business | Commercial business | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,191	753
Commercial Business | Commercial business | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	5	379
Residential real estate: | Residential mortgage
Financing Receivable, Past Due [Line Items]
Total loans	1,000,697	937,570
Residential real estate: | Residential mortgage | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	990,717	927,018
Residential real estate: | Residential mortgage | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	8,148	8,441
Loans greater than 90 days past due	296	557
Restructured loans	1,536	1,554
Total non-performing loans	9,980	10,552
Residential real estate: | Residential mortgage | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	983,787	919,199
Residential real estate: | Residential mortgage | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	5,331	5,157
Residential real estate: | Residential mortgage | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,599	2,662
Residential real estate: | Residential construction
Financing Receivable, Past Due [Line Items]
Total loans	204,259	197,652
Residential real estate: | Residential construction | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	204,208	197,597
Residential real estate: | Residential construction | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	51	55
Loans greater than 90 days past due	0	0
Restructured loans	0	0
Total non-performing loans	51	55
Residential real estate: | Residential construction | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	203,655	197,597
Residential real estate: | Residential construction | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	553	0
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	419,911	429,714
Consumer | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	413,505	422,989
Consumer | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	6,406	6,725
Loans greater than 90 days past due	0	0
Restructured loans	0	0
Total non-performing loans	6,406	6,725
Consumer | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	411,772	419,558
Consumer | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,577	3,021
Consumer | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	$ 156	$ 410