ALLOWANCE FOR CREDIT LOSSES AND CREDIT QUALITY INFORMATION - Schedule of Nonaccrual and Past Due Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024	Jun. 30, 2024
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans With No Allowance	$ 67,557	$ 103,578
Nonaccrual Loans With An Allowance	26,760	18,603
Total Loans	$ 12,989,546	$ 13,187,874	$ 13,141,390
Percent of nonaccrual loans with no allowance	0.52%	0.79%
Percent of nonaccrual loans with an allowance	0.21%	0.14%
% of Total Loans	100.00%	100.00%
Reverse mortgage, fair value	$ 4,700	$ 3,600	2,800
Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	$ 67,564	$ 44,768
Percent past due	0.52%	0.34%
30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	$ 45,349	$ 35,566
Percent past due	0.35%	0.27%
Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	$ 22,215	$ 9,202
Percent past due	0.17%	0.07%
Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Gross loans	$ 12,827,665	$ 13,020,925
Percent of accruing current balances	98.75%	98.73%
Commercial | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Gross loans	$ 2,744,392	$ 2,656,174
Nonaccrual Loans With No Allowance	27,557	43,206
Nonaccrual Loans With An Allowance	0	18,603
Total Loans	2,744,392	2,656,174	2,639,152
Commercial | Commercial and industrial | Discontinued Operations, Held-for-Sale
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans With No Allowance	10,900
Commercial | Commercial and industrial | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	13,586	1,970
Commercial | Commercial and industrial | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	11,014	1,482
Commercial | Commercial and industrial | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	2,572	488
Commercial | Commercial and industrial | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Gross loans	2,703,249	2,592,395
Commercial | Owner-occupied commercial
Financing Receivable, Past Due [Line Items]
Gross loans	1,947,594	1,973,645
Nonaccrual Loans With No Allowance	6,142	4,710
Nonaccrual Loans With An Allowance	0	0
Total Loans	1,947,594	1,973,645	1,940,677
Commercial | Owner-occupied commercial | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	13,403	902
Commercial | Owner-occupied commercial | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	6,617	706
Commercial | Owner-occupied commercial | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	6,786	196
Commercial | Owner-occupied commercial | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Gross loans	1,928,049	1,968,033
Commercial | Commercial mortgages
Financing Receivable, Past Due [Line Items]
Gross loans	3,911,537	4,030,627
Nonaccrual Loans With No Allowance	2,790	22,223
Nonaccrual Loans With An Allowance	21,325	0
Total Loans	3,911,537	4,030,627	4,034,818
Commercial | Commercial mortgages | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	4,472	3,183
Commercial | Commercial mortgages | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	3,479	2,621
Commercial | Commercial mortgages | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	993	562
Commercial | Commercial mortgages | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Gross loans	3,882,950	4,005,221
Commercial | Construction
Financing Receivable, Past Due [Line Items]
Gross loans	857,631	832,093
Nonaccrual Loans With No Allowance	23,070	25,600
Nonaccrual Loans With An Allowance	5,435	0
Total Loans	857,631	832,093	879,217
Commercial | Construction | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	1,715	0
Commercial | Construction | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	1,715	0
Commercial | Construction | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	0	0
Commercial | Construction | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Gross loans	827,411	806,493
Commercial | Commercial Small Business Leases
Financing Receivable, Past Due [Line Items]
Gross loans	630,127	647,516
Nonaccrual Loans With No Allowance	0	0
Nonaccrual Loans With An Allowance	0	0
Total Loans	630,127	647,516	643,520
Commercial | Commercial Small Business Leases | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	9,086	8,975
Commercial | Commercial Small Business Leases | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	9,086	8,409
Commercial | Commercial Small Business Leases | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	0	566
Commercial | Commercial Small Business Leases | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Gross loans	621,041	638,541
Residential
Financing Receivable, Past Due [Line Items]
Gross loans	981,140	965,051
Nonaccrual Loans With No Allowance	4,538	5,011
Nonaccrual Loans With An Allowance	0	0
Total Loans	976,462	961,426	897,573
Residential | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	4,621	4,277
Residential | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	4,546	4,262
Residential | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	75	15
Residential | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Gross loans	967,303	952,138
Consumer
Financing Receivable, Past Due [Line Items]
Gross loans	1,921,803	2,086,393
Nonaccrual Loans With No Allowance	3,460	2,828
Nonaccrual Loans With An Allowance	0	0
Total Loans	1,921,803	2,086,393	$ 2,106,433
Consumer | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	20,681	25,461
Consumer | Total Past Due And Still Accruing | Discontinued Operations, Held-for-Sale
Financing Receivable, Past Due [Line Items]
Gross loans	3,100
Consumer | 30–89 Days Past Due and Still  Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	8,892	18,086
Consumer | Greater  Than 90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	11,789	7,375
Consumer | Accruing Current Balances
Financing Receivable, Past Due [Line Items]
Gross loans	1,897,662	2,058,104
Consumer | Student loans | Total Past Due And Still Accruing
Financing Receivable, Past Due [Line Items]
Gross loans	$ 17,200	$ 15,600