LOANS AND ALLOWANCE FOR CREDIT LOSSES - Risk Rating (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024 USD ($) grade	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)
Loans by risk rating
Number of grades utilized in internal loan rating system | grade	10
Year one, originated current fiscal year	$ 50,777		$ 407,241
Year two, originated fiscal year before current fiscal year	413,307		1,443,688
Year three, originated two years before current fiscal year	1,453,571		1,092,960
Year four, originated three years before current fiscal year	1,086,176		513,582
Year five, originated four years before current fiscal year	507,310		308,448
Prior	1,022,383		739,967
Revolving Loans Amortized Cost	242,360		242,063
Revolving Loans Converted to Term Loans	1,337		1,469
Total loans before basis adjustment	4,777,221		4,749,418
YTD gross charge-offs, originated current fiscal year			31
YTD gross charge-offs, originated fiscal year before current fiscal year	14		129
YTD gross charge-offs, originated two years before current fiscal year	158		18
YTD gross charge-offs, originated three years before current fiscal year	84		20
YTD gross charge-offs, originated four years before current fiscal year	3		26
YTD gross charge-offs, prior	18		4,202
YTD gross charge-offs	277	$ 14	4,426
Commercial | Commercial real estate
Loans by risk rating
Year one, originated current fiscal year	24,559		152,047
Year two, originated fiscal year before current fiscal year	148,800		839,306
Year three, originated two years before current fiscal year	845,721		455,996
Year four, originated three years before current fiscal year	455,253		238,885
Year five, originated four years before current fiscal year	237,484		242,690
Prior	643,855		414,751
Total loans before basis adjustment	2,355,672		2,343,675
YTD gross charge-offs, prior			4,171
YTD gross charge-offs			4,171
Commercial | Commercial real estate | Pass
Loans by risk rating
Year one, originated current fiscal year	24,559		152,047
Year two, originated fiscal year before current fiscal year	147,200		828,335
Year three, originated two years before current fiscal year	826,882		455,996
Year four, originated three years before current fiscal year	455,253		234,585
Year five, originated four years before current fiscal year	233,191		233,713
Prior	614,772		405,103
Total loans before basis adjustment	2,301,857		2,309,779
Commercial | Commercial real estate | Special mention
Loans by risk rating
Year two, originated fiscal year before current fiscal year	1,600		10,971
Year three, originated two years before current fiscal year	18,839
Year four, originated three years before current fiscal year			4,300
Year five, originated four years before current fiscal year	4,293		8,977
Prior	27,587		2,232
Total loans before basis adjustment	52,319		26,480
Commercial | Commercial real estate | Substandard
Loans by risk rating
Prior	1,496		1,670
Total loans before basis adjustment	1,496		1,670
Commercial | Commercial real estate | Doubtful
Loans by risk rating
Prior			5,746
Total loans before basis adjustment			5,746
Commercial | Commercial construction
Loans by risk rating
Year one, originated current fiscal year			35,181
Year two, originated fiscal year before current fiscal year	49,916		111,881
Year three, originated two years before current fiscal year	119,906		60,113
Year four, originated three years before current fiscal year	64,268		843
Revolving Loans Amortized Cost	721		425
Total loans before basis adjustment	234,811		208,443
Commercial | Commercial construction | Pass
Loans by risk rating
Year one, originated current fiscal year			35,181
Year two, originated fiscal year before current fiscal year	45,676		109,291
Year three, originated two years before current fiscal year	110,181		60,113
Year four, originated three years before current fiscal year	64,268		843
Revolving Loans Amortized Cost	721		425
Total loans before basis adjustment	220,846		205,853
Commercial | Commercial construction | Special mention
Loans by risk rating
Year two, originated fiscal year before current fiscal year	4,240		2,590
Year three, originated two years before current fiscal year	9,725
Total loans before basis adjustment	13,965		2,590
Commercial | Commercial and industrial
Loans by risk rating
Year one, originated current fiscal year	11,690		73,240
Year two, originated fiscal year before current fiscal year	73,215		52,696
Year three, originated two years before current fiscal year	51,132		94,582
Year four, originated three years before current fiscal year	92,860		70,588
Year five, originated four years before current fiscal year	68,977		22,990
Prior	97,012		78,105
Revolving Loans Amortized Cost	76,329		74,242
Total loans before basis adjustment	471,215		466,443
YTD gross charge-offs, originated current fiscal year			24
YTD gross charge-offs, originated fiscal year before current fiscal year			113
YTD gross charge-offs, originated two years before current fiscal year	153		14
YTD gross charge-offs, originated three years before current fiscal year	65		5
YTD gross charge-offs, originated four years before current fiscal year	3		8
YTD gross charge-offs, prior	7		2
YTD gross charge-offs	228	7	166
Commercial | Commercial and industrial | Pass
Loans by risk rating
Year one, originated current fiscal year	11,690		73,240
Year two, originated fiscal year before current fiscal year	73,215		52,190
Year three, originated two years before current fiscal year	50,703		94,570
Year four, originated three years before current fiscal year	92,676		70,565
Year five, originated four years before current fiscal year	68,905		22,988
Prior	94,486		75,493
Revolving Loans Amortized Cost	76,180		74,125
Total loans before basis adjustment	467,855		463,171
Commercial | Commercial and industrial | Special mention
Loans by risk rating
Year two, originated fiscal year before current fiscal year			454
Year three, originated two years before current fiscal year	427		4
Year four, originated three years before current fiscal year	184		23
Year five, originated four years before current fiscal year	22		2
Prior	883		948
Revolving Loans Amortized Cost	100		50
Total loans before basis adjustment	1,616		1,481
Commercial | Commercial and industrial | Substandard
Loans by risk rating
Year two, originated fiscal year before current fiscal year			52
Year three, originated two years before current fiscal year	2		8
Year five, originated four years before current fiscal year	50
Prior	390		367
Revolving Loans Amortized Cost			18
Total loans before basis adjustment	442		445
Commercial | Commercial and industrial | Doubtful
Loans by risk rating
Prior	1,253		1,297
Revolving Loans Amortized Cost	49		49
Total loans before basis adjustment	1,302		1,346
Residential
Loans by risk rating
Year one, originated current fiscal year	12,179		138,541
Year two, originated fiscal year before current fiscal year	135,862		434,421
Year three, originated two years before current fiscal year	432,009		480,010
Year four, originated three years before current fiscal year	471,883		202,245
Year five, originated four years before current fiscal year	200,042		39,631
Prior	278,560		246,144
Revolving Loans Amortized Cost	164,350		166,360
Revolving Loans Converted to Term Loans	1,337		1,469
Total loans before basis adjustment	1,696,222		1,708,821
Residential | Accrual
Loans by risk rating
Year one, originated current fiscal year	12,179		138,541
Year two, originated fiscal year before current fiscal year	135,862		434,421
Year three, originated two years before current fiscal year	431,542		480,010
Year four, originated three years before current fiscal year	471,589		202,118
Year five, originated four years before current fiscal year	199,720		38,675
Prior	271,197		239,185
Revolving Loans Amortized Cost	163,938		166,144
Revolving Loans Converted to Term Loans	1,329		1,469
Total loans before basis adjustment	1,687,356		1,700,563
Residential | Nonaccrual
Loans by risk rating
Year three, originated two years before current fiscal year	467
Year four, originated three years before current fiscal year	294		127
Year five, originated four years before current fiscal year	322		956
Prior	7,363		6,959
Revolving Loans Amortized Cost	412		216
Revolving Loans Converted to Term Loans	8
Total loans before basis adjustment	8,866		8,258
Consumer loans
Loans by risk rating
Year one, originated current fiscal year	2,349		8,232
Year two, originated fiscal year before current fiscal year	5,514		5,384
Year three, originated two years before current fiscal year	4,803		2,259
Year four, originated three years before current fiscal year	1,912		1,021
Year five, originated four years before current fiscal year	807		3,137
Prior	2,956		967
Revolving Loans Amortized Cost	960		1,036
Total loans before basis adjustment	19,301		22,036
YTD gross charge-offs, originated current fiscal year			7
YTD gross charge-offs, originated fiscal year before current fiscal year	14		16
YTD gross charge-offs, originated two years before current fiscal year	5		4
YTD gross charge-offs, originated three years before current fiscal year	19		15
YTD gross charge-offs, originated four years before current fiscal year			18
YTD gross charge-offs, prior	11		29
YTD gross charge-offs	49	$ 7	89
Consumer loans | Accrual
Loans by risk rating
Year one, originated current fiscal year	2,349		8,218
Year two, originated fiscal year before current fiscal year	5,510		5,366
Year three, originated two years before current fiscal year	4,791		2,254
Year four, originated three years before current fiscal year	1,912		1,021
Year five, originated four years before current fiscal year	803		3,135
Prior	2,928		963
Revolving Loans Amortized Cost	954		1,031
Total loans before basis adjustment	19,247		21,988
Consumer loans | Nonaccrual
Loans by risk rating
Year one, originated current fiscal year			14
Year two, originated fiscal year before current fiscal year	4		18
Year three, originated two years before current fiscal year	12		5
Year five, originated four years before current fiscal year	4		2
Prior	28		4
Revolving Loans Amortized Cost	6		5
Total loans before basis adjustment	$ 54		$ 48