ALLOWANCE FOR CREDIT LOSSES AND CREDIT QUALITY INFORMATION - Schedule of Allowance for Loan Losses and Loan Balances (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Allowance for credit losses
Beginning balance	$ 192,629	$ 169,162	$ 186,126	$ 151,861	$ 151,861
Charge-offs	(17,572)	(15,874)	(29,431)	(29,540)
Recoveries	3,381	2,750	6,605	4,705
Provision	19,815	15,831	34,953	44,843
Ending balance	198,253	171,869	198,253	171,869	186,126
Period-end allowance allocated to:
Loans evaluated on an individual basis	8,055	1,953	8,055	1,953
Loans evaluated on a collective basis	190,198	169,916	190,198	169,916
Period-end loan balances:
Loans evaluated on an individual basis	67,493	39,268	67,493	39,268
Loans evaluated on a collective basis	13,073,897	12,297,566	13,073,897	12,297,566
Ending balance	13,141,390	12,336,834	13,141,390	12,336,834	12,766,518
Reverse mortgage, fair value	2,800	3,100	2,800	3,100	2,800
Commercial | Commercial and industrial
Allowance for credit losses
Beginning balance	55,902	53,473	49,394	49,526	49,526
Charge-offs	(1,906)	(6,453)	(2,382)	(13,016)	(26,653)
Recoveries	1,736	1,814	3,502	2,515
Provision	784	3,566	6,002	13,375
Ending balance	56,516	52,400	56,516	52,400	49,394
Period-end allowance allocated to:
Loans evaluated on an individual basis	8,055	1,953	8,055	1,953
Loans evaluated on a collective basis	48,461	50,447	48,461	50,447
Period-end loan balances:
Loans evaluated on an individual basis	39,217	18,367	39,217	18,367
Loans evaluated on a collective basis	2,599,935	2,605,356	2,599,935	2,605,356
Ending balance	2,639,152	2,623,723	2,639,152	2,623,723	2,540,070
Commercial | Owner-occupied commercial
Allowance for credit losses
Beginning balance	10,569	6,056	10,719	6,019	6,019
Charge-offs	0	(184)	0	(184)	(184)
Recoveries	4	31	205	36
Provision	(905)	432	(1,256)	464
Ending balance	9,668	6,335	9,668	6,335	10,719
Period-end allowance allocated to:
Loans evaluated on an individual basis	0	0	0	0
Loans evaluated on a collective basis	9,668	6,335	9,668	6,335
Period-end loan balances:
Loans evaluated on an individual basis	4,260	3,979	4,260	3,979
Loans evaluated on a collective basis	1,936,417	1,879,076	1,936,417	1,879,076
Ending balance	1,940,677	1,883,055	1,940,677	1,883,055	1,886,087
Commercial | Commercial mortgages
Allowance for credit losses
Beginning balance	36,797	30,114	36,055	21,473	21,473
Charge-offs	(4,907)	0	(4,932)	0	(300)
Recoveries	102	1	104	3
Provision	14,839	1,822	15,604	10,461
Ending balance	46,831	31,937	46,831	31,937	36,055
Period-end allowance allocated to:
Loans evaluated on an individual basis	0	0	0	0
Loans evaluated on a collective basis	46,831	31,937	46,831	31,937
Period-end loan balances:
Loans evaluated on an individual basis	8,991	7,515	8,991	7,515
Loans evaluated on a collective basis	4,025,827	3,545,285	4,025,827	3,545,285
Ending balance	4,034,818	3,552,800	4,034,818	3,552,800	3,801,180
Commercial | Construction
Allowance for credit losses
Beginning balance	10,959	9,672	10,762	6,987	6,987
Charge-offs	0	0	0	0	(794)
Recoveries	0	1	0	531
Provision	(1,761)	(445)	(1,564)	1,710
Ending balance	9,198	9,228	9,198	9,228	10,762
Period-end allowance allocated to:
Loans evaluated on an individual basis	0	0	0	0
Loans evaluated on a collective basis	9,198	9,228	9,198	9,228
Period-end loan balances:
Loans evaluated on an individual basis	3,887	741	3,887	741
Loans evaluated on a collective basis	875,330	954,483	875,330	954,483
Ending balance	879,217	955,224	879,217	955,224	1,035,530
Commercial | Commercial Small Business Leases
Allowance for credit losses
Beginning balance	15,459	9,236	15,170	9,868	9,868
Charge-offs	(4,888)	(3,906)	(9,740)	(6,805)	(15,641)
Recoveries	831	400	1,422	915
Provision	4,816	4,653	9,366	6,405
Ending balance	16,218	10,383	16,218	10,383	15,170
Period-end allowance allocated to:
Loans evaluated on an individual basis	0	0	0	0
Loans evaluated on a collective basis	16,218	10,383	16,218	10,383
Period-end loan balances:
Loans evaluated on an individual basis	0	0	0	0
Loans evaluated on a collective basis	643,520	590,063	643,520	590,063
Ending balance	643,520	590,063	643,520	590,063	623,622
Residential
Allowance for credit losses
Beginning balance	5,407	5,327	5,483	4,668	4,668
Charge-offs	(51)	(33)	(101)	(33)	(41)
Recoveries	43	113	132	156
Provision	(342)	(364)	(457)	252
Ending balance	5,057	5,043	5,057	5,043	5,483
Period-end allowance allocated to:
Loans evaluated on an individual basis	0	0	0	0
Loans evaluated on a collective basis	5,057	5,043	5,057	5,043
Period-end loan balances:
Loans evaluated on an individual basis	8,300	6,491	8,300	6,491
Loans evaluated on a collective basis	889,273	820,259	889,273	820,259
Ending balance	897,573	826,750	897,573	826,750	867,895
Consumer
Allowance for credit losses
Beginning balance	57,536	55,284	58,543	53,320	53,320
Charge-offs	(5,820)	(5,298)	(12,276)	(9,502)	(22,394)
Recoveries	665	390	1,240	549
Provision	2,384	6,167	7,258	12,176
Ending balance	54,765	56,543	54,765	56,543	58,543
Period-end allowance allocated to:
Loans evaluated on an individual basis	0	0	0	0
Loans evaluated on a collective basis	54,765	56,543	54,765	56,543
Period-end loan balances:
Loans evaluated on an individual basis	2,838	2,175	2,838	2,175
Loans evaluated on a collective basis	2,103,595	1,903,044	2,103,595	1,903,044
Ending balance	$ 2,106,433	$ 1,905,219	$ 2,106,433	$ 1,905,219	$ 2,012,134