ALLOWANCE FOR CREDIT LOSSES AND CREDIT QUALITY INFORMATION - Schedule of Nonaccrual and Past Due Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans With No Allowance	$ 38,215	$ 58,441
Nonaccrual Loans With An Allowance	25,819	5,568
Gross loans	$ 13,141,390	$ 12,766,518	$ 12,336,834
Percent of nonaccrual loans with no allowance	0.29%	0.46%
Percent of nonaccrual loans with an allowance	0.20%	0.04%
% of Total Loans	100.00%	100.00%
Reverse mortgage, fair value	$ 2,800	$ 2,800	3,100
Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	$ 49,957	$ 47,397
Percent past due	0.38%	0.37%
30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	$ 40,159	$ 35,813
Percent past due	0.31%	0.28%
Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	$ 9,798	$ 11,584
Percent past due	0.07%	0.09%
Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Total Loans	$ 13,027,399	$ 12,655,112
Percent of accruing current balances	99.13%	99.13%
Residential
Financing Receivable, Past Due [Line Items]
Total Loans	$ 900,384	$ 870,705
Nonaccrual Loans With No Allowance	5,086	2,579
Nonaccrual Loans With An Allowance	0	0
Gross loans	897,573	867,895	826,750
Residential | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	4,595	9,261
Residential | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	4,587	9,261
Residential | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	8	0
Residential | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Total Loans	887,892	856,055
Consumer
Financing Receivable, Past Due [Line Items]
Total Loans	2,106,433	2,012,134
Nonaccrual Loans With No Allowance	2,903	2,446
Nonaccrual Loans With An Allowance	0	0
Gross loans	2,106,433	2,012,134	1,905,219
Consumer | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	22,975	25,281
Consumer | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	14,040	15,249
Consumer | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	8,935	10,032
Consumer | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Total Loans	2,080,555	1,984,407
Commercial and industrial | Commercial
Financing Receivable, Past Due [Line Items]
Total Loans	2,639,152	2,540,070
Nonaccrual Loans With No Allowance	13,411	13,645
Nonaccrual Loans With An Allowance	25,819	5,568
Gross loans	2,639,152	2,540,070	2,623,723
Commercial and industrial | Commercial | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	5,215	1,923
Commercial and industrial | Commercial | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	4,456	1,630
Commercial and industrial | Commercial | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	759	293
Commercial and industrial | Commercial | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Total Loans	2,594,707	2,518,934
Owner-occupied commercial | Commercial
Financing Receivable, Past Due [Line Items]
Total Loans	1,940,677	1,886,087
Nonaccrual Loans With No Allowance	3,939	4,862
Nonaccrual Loans With An Allowance	0	0
Gross loans	1,940,677	1,886,087	1,883,055
Owner-occupied commercial | Commercial | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	5,196	2,273
Owner-occupied commercial | Commercial | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	5,196	1,786
Owner-occupied commercial | Commercial | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	0	487
Owner-occupied commercial | Commercial | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Total Loans	1,931,542	1,878,952
Commercial mortgages | Commercial
Financing Receivable, Past Due [Line Items]
Total Loans	4,034,818	3,801,180
Nonaccrual Loans With No Allowance	8,989	22,292
Nonaccrual Loans With An Allowance	0	0
Gross loans	4,034,818	3,801,180	3,552,800
Commercial mortgages | Commercial | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	1,720	1,190
Commercial mortgages | Commercial | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	1,674	1,190
Commercial mortgages | Commercial | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	46	0
Commercial mortgages | Commercial | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Total Loans	4,024,109	3,777,698
Construction | Commercial
Financing Receivable, Past Due [Line Items]
Total Loans	879,217	1,035,530
Nonaccrual Loans With No Allowance	3,887	12,617
Nonaccrual Loans With An Allowance	0	0
Gross loans	879,217	1,035,530	955,224
Construction | Commercial | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Construction | Commercial | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Construction | Commercial | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Construction | Commercial | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Total Loans	875,330	1,022,913
Commercial Small Business Leases | Commercial
Financing Receivable, Past Due [Line Items]
Total Loans	643,520	623,622
Nonaccrual Loans With No Allowance	0	0
Nonaccrual Loans With An Allowance	0	0
Gross loans	643,520	623,622	$ 590,063
Commercial Small Business Leases | Commercial | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	10,256	7,469
Commercial Small Business Leases | Commercial | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	10,206	6,697
Commercial Small Business Leases | Commercial | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	50	772
Commercial Small Business Leases | Commercial | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Total Loans	633,264	616,153
Student loans | Consumer | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	$ 11,900	$ 14,500