ALLOWANCE FOR CREDIT LOSSES AND CREDIT QUALITY INFORMATION - Allowance for Loan Losses and Loan Balances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Allowance for credit losses
Beginning balance	$ 186,126	$ 151,861	$ 94,507
Charge-offs	(65,123)	(66,007)	(27,470)
Recoveries	12,867	12,199	10,638
Provision (release)	61,411	88,073	48,083
Ending balance	195,281	186,126	151,861
Loans evaluated on an individual basis	8,349	1,591	2,428
Loans evaluated on a collective basis	186,932	184,535	149,433
Loans evaluated on an individual basis	125,612	67,496	40,740
Loans evaluated on a collective basis	13,062,262	12,699,022	11,868,696
Ending balance	13,187,874	12,766,518	11,909,436
Reverse mortgage, fair value	3,600	2,800	2,400
Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for credit losses
Beginning balance			26,103
BMBC
Allowance for credit losses
Loans purchased with no credit deterioration			23,500
Commercial | Commercial and industrial
Allowance for credit losses
Beginning balance	49,394	49,526	43,987
Charge-offs	(15,490)	(26,653)	(12,500)
Recoveries	6,883	7,735	4,806
Provision (release)	16,344	18,786	(9,380)
Ending balance	57,131	49,394	49,526
Loans evaluated on an individual basis	8,349	1,591	2,428
Loans evaluated on a collective basis	48,782	47,803	47,098
Loans evaluated on an individual basis	61,674	19,221	17,572
Loans evaluated on a collective basis	2,594,500	2,520,849	2,557,773
Ending balance	2,656,174	2,540,070	2,575,345
Commercial | Commercial and industrial | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for credit losses
Beginning balance			22,613
Commercial | Owner-occupied commercial
Allowance for credit losses
Beginning balance	10,719	6,019	4,574
Charge-offs	(177)	(184)	(179)
Recoveries	217	54	278
Provision (release)	(1,620)	4,830	751
Ending balance	9,139	10,719	6,019
Loans evaluated on an individual basis	0	0	0
Loans evaluated on a collective basis	9,139	10,719	6,019
Loans evaluated on an individual basis	5,010	5,200	1,929
Loans evaluated on a collective basis	1,968,635	1,880,887	1,807,653
Ending balance	1,973,645	1,886,087	1,809,582
Commercial | Owner-occupied commercial | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for credit losses
Beginning balance			595
Commercial | Commercial mortgages
Allowance for credit losses
Beginning balance	36,055	21,473	11,623
Charge-offs	(5,749)	(300)	(581)
Recoveries	183	7	223
Provision (release)	18,473	14,875	7,524
Ending balance	48,962	36,055	21,473
Loans evaluated on an individual basis	0	0	0
Loans evaluated on a collective basis	48,962	36,055	21,473
Loans evaluated on an individual basis	22,223	22,295	6,369
Loans evaluated on a collective basis	4,008,404	3,778,885	3,344,715
Ending balance	4,030,627	3,801,180	3,351,084
Commercial | Commercial mortgages | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for credit losses
Beginning balance			2,684
Commercial | Construction
Allowance for credit losses
Beginning balance	10,762	6,987	1,903
Charge-offs	0	(794)	0
Recoveries	0	532	2,567
Provision (release)	(1,577)	4,037	2,446
Ending balance	9,185	10,762	6,987
Loans evaluated on an individual basis	0	0	0
Loans evaluated on a collective basis	9,185	10,762	6,987
Loans evaluated on an individual basis	25,600	12,617	5,143
Loans evaluated on a collective basis	806,493	1,022,913	1,038,906
Ending balance	832,093	1,035,530	1,044,049
Commercial | Construction | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for credit losses
Beginning balance			71
Commercial | Commercial small business leases
Allowance for credit losses
Beginning balance	15,170	9,868	5,980
Charge-offs	(20,033)	(15,641)	(6,504)
Recoveries	2,705	1,986	1,306
Provision (release)	18,123	18,957	9,085
Ending balance	15,965	15,170	9,868
Loans evaluated on an individual basis	0	0	0
Loans evaluated on a collective basis	15,965	15,170	9,868
Loans evaluated on an individual basis	0	0	0
Loans evaluated on a collective basis	647,516	623,622	558,981
Ending balance	647,516	623,622	558,981
Commercial | Commercial small business leases | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for credit losses
Beginning balance			1
Residential
Allowance for credit losses
Beginning balance	5,483	4,668	3,352
Charge-offs	(125)	(41)	(186)
Recoveries	225	260	665
Provision (release)	(17)	596	776
Ending balance	5,566	5,483	4,668
Loans evaluated on an individual basis	0	0	0
Loans evaluated on a collective basis	5,566	5,483	4,668
Loans evaluated on an individual basis	8,315	5,876	7,680
Loans evaluated on a collective basis	953,111	862,019	751,785
Ending balance	961,426	867,895	759,465
Residential | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for credit losses
Beginning balance			61
Consumer
Allowance for credit losses
Beginning balance	58,543	53,320	23,088
Charge-offs	(23,549)	(22,394)	(7,520)
Recoveries	2,654	1,625	793
Provision (release)	11,685	25,992	36,881
Ending balance	49,333	58,543	53,320
Loans evaluated on an individual basis	0	0	0
Loans evaluated on a collective basis	49,333	58,543	53,320
Loans evaluated on an individual basis	2,790	2,287	2,047
Loans evaluated on a collective basis	2,083,603	2,009,847	1,808,883
Ending balance	$ 2,086,393	$ 2,012,134	1,810,930
Consumer | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for credit losses
Beginning balance			$ 78