ALLOWANCE FOR CREDIT LOSSES AND CREDIT QUALITY INFORMATION - Schedule of Nonaccrual and Past Due Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans With No Allowance	$ 51,685	$ 58,441
Nonaccrual Loans With An Allowance	14,263	5,568
Gross loans	$ 12,980,281	$ 12,766,518	$ 12,143,268
Percent of nonaccrual loans with no allowance	0.40%	0.46%
Percent of nonaccrual loans with allowance	0.11%	0.04%
% of Total Loans	100.00%	100.00%
Reverse mortgage, fair value	$ 2,500	$ 2,800	2,700
Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	$ 56,080	$ 47,397
Percent past due	0.43%	0.37%
30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	$ 44,718	$ 35,813
Percent past due	0.34%	0.28%
Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	$ 11,362	$ 11,584
Percent past due	0.09%	0.09%
Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Total Loans	$ 12,858,253	$ 12,655,112
Percent of accruing current balances	99.06%	99.13%
Residential
Financing Receivable, Past Due [Line Items]
Total Loans	$ 875,141	$ 870,705
Nonaccrual Loans With No Allowance	5,188	2,579
Nonaccrual Loans With An Allowance	0	0
Gross loans	872,665	867,895	786,060
Residential | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	1,793	9,261
Residential | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	1,793	9,261
Residential | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Residential | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Total Loans	865,684	856,055
Consumer
Financing Receivable, Past Due [Line Items]
Total Loans	2,065,871	2,012,134
Nonaccrual Loans With No Allowance	2,688	2,446
Nonaccrual Loans With An Allowance	0	0
Gross loans	2,065,871	2,012,134	1,868,427
Consumer | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	27,772	25,281
Consumer | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	17,651	15,249
Consumer | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	10,121	10,032
Consumer | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Total Loans	2,035,411	1,984,407
Commercial and industrial | Commercial
Financing Receivable, Past Due [Line Items]
Total Loans	2,591,861	2,540,070
Nonaccrual Loans With No Allowance	12,987	13,645
Nonaccrual Loans With An Allowance	14,263	5,568
Gross loans	2,591,861	2,540,070	2,568,742
Commercial and industrial | Commercial | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	3,264	1,923
Commercial and industrial | Commercial | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	2,674	1,630
Commercial and industrial | Commercial | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	590	293
Commercial and industrial | Commercial | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Total Loans	2,561,347	2,518,934
Owner-occupied commercial | Commercial
Financing Receivable, Past Due [Line Items]
Total Loans	1,882,876	1,886,087
Nonaccrual Loans With No Allowance	5,326	4,862
Nonaccrual Loans With An Allowance	0	0
Gross loans	1,882,876	1,886,087	1,846,661
Owner-occupied commercial | Commercial | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	4,181	2,273
Owner-occupied commercial | Commercial | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	3,582	1,786
Owner-occupied commercial | Commercial | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	599	487
Owner-occupied commercial | Commercial | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Total Loans	1,873,369	1,878,952
Commercial mortgages | Commercial
Financing Receivable, Past Due [Line Items]
Total Loans	3,876,856	3,801,180
Nonaccrual Loans With No Allowance	21,534	22,292
Nonaccrual Loans With An Allowance	0	0
Gross loans	3,876,856	3,801,180	3,473,083
Commercial mortgages | Commercial | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	1,915	1,190
Commercial mortgages | Commercial | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	1,866	1,190
Commercial mortgages | Commercial | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	49	0
Commercial mortgages | Commercial | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Total Loans	3,853,407	3,777,698
Construction | Commercial
Financing Receivable, Past Due [Line Items]
Total Loans	1,056,349	1,035,530
Nonaccrual Loans With No Allowance	3,962	12,617
Nonaccrual Loans With An Allowance	0	0
Gross loans	1,056,349	1,035,530	1,023,711
Construction | Commercial | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	7,343	0
Construction | Commercial | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	7,343	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	1,045,044	1,022,913
Commercial Small Business Leases | Commercial
Financing Receivable, Past Due [Line Items]
Total Loans	633,803	623,622
Nonaccrual Loans With No Allowance	0	0
Nonaccrual Loans With An Allowance	0	0
Gross loans	633,803	623,622	$ 576,584
Commercial Small Business Leases | Commercial | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	9,812	7,469
Commercial Small Business Leases | Commercial | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	9,809	6,697
Commercial Small Business Leases | Commercial | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	3	772
Commercial Small Business Leases | Commercial | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Total Loans	623,991	616,153
Student loans | Consumer | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Total Loans	$ 16,100	$ 14,500