CREDIT QUALITY ASSESSMENT - Credit Quality of Loan Portfolio (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Past Due [Line Items]
Total loans	$ 11,364,284	$ 11,366,989
Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	11,279,843	11,275,142
Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	84,081	91,485
Loans greater than 90 days past due	360	362
Total loans	84,441	91,847
Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	11,238,334	11,248,749
30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	32,737	23,732
60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	8,772	2,661
Commercial investor real estate
Financing Receivable, Past Due [Line Items]
Total loans	4,997,879	5,104,425
Commercial owner-occupied real estate
Financing Receivable, Past Due [Line Items]
Total loans	1,741,113	1,755,235
Commercial AD&C
Financing Receivable, Past Due [Line Items]
Total loans	1,090,259	988,967
Residential mortgage
Financing Receivable, Past Due [Line Items]
Total loans	1,511,624	1,474,521
Residential construction
Financing Receivable, Past Due [Line Items]
Total loans	97,685	121,419
Commercial real estate: | Commercial investor real estate
Financing Receivable, Past Due [Line Items]
Total loans	4,997,879	5,104,425
Commercial real estate: | Commercial investor real estate | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	4,942,300	5,045,767
Commercial real estate: | Commercial investor real estate | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	55,579	58,658
Loans greater than 90 days past due	0	0
Total loans	55,579	58,658
Commercial real estate: | Commercial investor real estate | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	4,932,570	5,044,647
Commercial real estate: | Commercial investor real estate | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	9,681	1,120
Commercial real estate: | Commercial investor real estate | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	49	0
Commercial real estate: | Commercial owner-occupied real estate
Financing Receivable, Past Due [Line Items]
Total loans	1,741,113	1,755,235
Commercial real estate: | Commercial owner-occupied real estate | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,736,719	1,750,595
Commercial real estate: | Commercial owner-occupied real estate | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	4,394	4,640
Loans greater than 90 days past due	0	0
Total loans	4,394	4,640
Commercial real estate: | Commercial owner-occupied real estate | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,729,205	1,748,449
Commercial real estate: | Commercial owner-occupied real estate | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,538	2,056
Commercial real estate: | Commercial owner-occupied real estate | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	5,976	90
Commercial real estate: | Commercial AD&C
Financing Receivable, Past Due [Line Items]
Total loans	1,090,259	988,967
Commercial real estate: | Commercial AD&C | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,089,703	987,708
Commercial real estate: | Commercial AD&C | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	556	1,259
Loans greater than 90 days past due	0	0
Total loans	556	1,259
Commercial real estate: | Commercial AD&C | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,083,907	986,859
Commercial real estate: | Commercial AD&C | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	5,796	849
Commercial real estate: | Commercial AD&C | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	0	0
Commercial Business
Financing Receivable, Past Due [Line Items]
Total loans	9,338,843	9,353,507
Commercial Business | Commercial business
Financing Receivable, Past Due [Line Items]
Total loans	1,509,592	1,504,880
Commercial Business | Commercial business | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,502,408	1,494,809
Commercial Business | Commercial business | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	7,164	10,051
Loans greater than 90 days past due	20	20
Total loans	7,184	10,071
Commercial Business | Commercial business | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,499,245	1,494,426
Commercial Business | Commercial business | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,658	383
Commercial Business | Commercial business | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,505	0
Residential real estate: | Residential mortgage
Financing Receivable, Past Due [Line Items]
Total loans	1,511,624	1,474,521
Residential real estate: | Residential mortgage | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,499,449	1,461,847
Residential real estate: | Residential mortgage | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	11,835	12,332
Loans greater than 90 days past due	340	342
Total loans	12,175	12,674
Residential real estate: | Residential mortgage | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	1,486,341	1,445,785
Residential real estate: | Residential mortgage | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	12,336	14,026
Residential real estate: | Residential mortgage | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	772	2,036
Residential real estate: | Residential construction
Financing Receivable, Past Due [Line Items]
Total loans	97,685	121,419
Residential real estate: | Residential construction | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	97,143	120,976
Residential real estate: | Residential construction | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	542	443
Loans greater than 90 days past due	0	0
Total loans	542	443
Residential real estate: | Residential construction | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	96,404	118,976
Residential real estate: | Residential construction | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	739	2,000
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	416,132	417,542
Consumer | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	412,121	413,440
Consumer | Non-performing loans:
Financing Receivable, Past Due [Line Items]
Non-accrual loans	4,011	4,102
Loans greater than 90 days past due	0	0
Total loans	4,011	4,102
Consumer | Current | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	410,662	409,607
Consumer | 30-59 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	989	3,298
Consumer | 60-89 days | Performing loans:
Financing Receivable, Past Due [Line Items]
Total loans	$ 470	$ 535