LOANS AND ALLOWANCE FOR LOAN LOSSES - Allowances (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2016
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance	$ 21,161
Charge-offs	(571)	$ (444)
Recoveries	91	111
Net recoveries (charge-offs)	(480)	(333)
Provision	709	1,040
Ending balance	21,390	14,960
Ending allowance balance attributable to loans [Abstract]
Individually evaluated for impairment			$ 5,681	$ 5,937
Collectively evaluated for impairment			15,709	15,195
Total ending allowance balance	21,161	14,960	21,390	21,161	$ 21,161	$ 14,253
Loans [Abstract]
Loans individually evaluated for impairment			13,640	13,926
Loans collectively evaluated for impairment			1,309,889	1,300,864
Total ending loans balance			1,323,529	1,315,582
Loans acquired with deteriorated credit quality
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance	29
Ending balance
Ending allowance balance attributable to loans [Abstract]
Total ending allowance balance	29			29
Loans [Abstract]
Total ending loans balance			0	792
Commercial and agricultural:
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance	6,976
Charge-offs	(19)	(5)
Recoveries	9	24
Net recoveries (charge-offs)	(10)	19
Provision	37	42
Ending balance	7,003	1,650
Ending allowance balance attributable to loans [Abstract]
Individually evaluated for impairment			4,910	5,135
Collectively evaluated for impairment			2,093	1,841
Total ending allowance balance	6,976	1,650	7,003	6,976	6,976	1,589
Loans [Abstract]
Loans individually evaluated for impairment			5,795	6,133
Loans collectively evaluated for impairment			195,242	193,443
Total ending loans balance			201,037	199,576
Commercial and agricultural: | Loans acquired with deteriorated credit quality
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance	0
Ending balance
Ending allowance balance attributable to loans [Abstract]
Total ending allowance balance	0			0
Loans [Abstract]
Total ending loans balance				0
Commercial Mortgages
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance	8,514
Charge-offs	0	0
Recoveries	1	1
Net recoveries (charge-offs)	1	1
Provision	125	478
Ending balance	8,640	7,749
Ending allowance balance attributable to loans [Abstract]
Individually evaluated for impairment			771	802
Collectively evaluated for impairment			7,869	7,683
Total ending allowance balance	8,514	7,749	8,640	8,514	8,514	7,270
Loans [Abstract]
Loans individually evaluated for impairment			7,359	7,302
Loans collectively evaluated for impairment			642,054	638,080
Total ending loans balance			649,413	646,174
Commercial Mortgages | Loans acquired with deteriorated credit quality
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance	29
Ending balance
Ending allowance balance attributable to loans [Abstract]
Total ending allowance balance	29			29
Loans [Abstract]
Total ending loans balance				792
Residential mortgages
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance	1,316
Charge-offs	(94)	(12)
Recoveries	5	17
Net recoveries (charge-offs)	(89)	5
Provision	180	(16)
Ending balance	1,407	1,512
Ending allowance balance attributable to loans [Abstract]
Individually evaluated for impairment			0	0
Collectively evaluated for impairment			1,407	1,316
Total ending allowance balance	1,316	1,512	1,407	1,316	1,316	1,523
Loans [Abstract]
Loans individually evaluated for impairment			425	427
Loans collectively evaluated for impairment			194,671	194,510
Total ending loans balance			195,096	194,937
Residential mortgages | Loans acquired with deteriorated credit quality
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance	0
Ending balance
Ending allowance balance attributable to loans [Abstract]
Total ending allowance balance	0			0
Loans [Abstract]
Total ending loans balance			0	0
Consumer loans:
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance	4,355
Charge-offs	(458)	(427)
Recoveries	76	69
Net recoveries (charge-offs)	(382)	(358)
Provision	367	536
Ending balance	4,340	4,049
Ending allowance balance attributable to loans [Abstract]
Individually evaluated for impairment			0	0
Collectively evaluated for impairment			4,340	4,355
Total ending allowance balance	4,355	$ 4,049	4,340	4,355	$ 4,355	$ 3,871
Loans [Abstract]
Loans individually evaluated for impairment			61	64
Loans collectively evaluated for impairment			277,922	274,831
Total ending loans balance			$ 277,983	274,895
Consumer loans: | Loans acquired with deteriorated credit quality
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance	0
Ending balance
Ending allowance balance attributable to loans [Abstract]
Total ending allowance balance	$ 0			0
Loans [Abstract]
Total ending loans balance				$ 0