ACCUMULATED OTHER COMPREHENSIVE INCOME OR LOSS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary of changes in accumulated other comprehensive income or loss by component, net of tax [Roll Forward]
Beginning Balances	$ 143,748	$ 137,242	$ 133,628
Stranded AOCI reclassification	0
Total other comprehensive income (loss)	2,251	188	(2,157)
Ending Balances	149,813	143,748	137,242
Net gains on securities transactions	109	987	372
Income tax expense	7,262	4,404	4,658
Pension and other employee benefits	4,276	6,132	5,908
Net of tax	7,430	10,027	9,433
Reclassification out of Accumulated Other Comprehensive Income (loss)
Summary of changes in accumulated other comprehensive income or loss by component, net of tax [Roll Forward]
Net of tax	51	799	631
Unrealized Gains and Losses on Securities Available for Sale
Summary of changes in accumulated other comprehensive income or loss by component, net of tax [Roll Forward]
Beginning Balances	(4,356)	210	1,960
Other comprehensive income (loss) before reclassification	1,578	(3,952)	(1,520)
Amounts reclassified from accumulated other comprehensive income (loss)	(68)	(614)	(230)
Stranded AOCI reclassification	(569)
Total other comprehensive income (loss)	1,510	(4,566)	(1,750)
Ending Balances	(3,415)	(4,356)	210
Unrealized Gains and Losses on Securities Available for Sale | Reclassification out of Accumulated Other Comprehensive Income (loss)
Summary of changes in accumulated other comprehensive income or loss by component, net of tax [Roll Forward]
Net gains on securities transactions	(109)	(987)	(372)
Income tax expense	41	373	142
Net of tax	(68)	(614)	(230)
Defined Benefit and Other Benefit Plans
Summary of changes in accumulated other comprehensive income or loss by component, net of tax [Roll Forward]
Beginning Balances	(6,398)	(11,152)	(10,745)
Other comprehensive income (loss) before reclassification	622	3,341	(1,268)
Amounts reclassified from accumulated other comprehensive income (loss)	119	1,413	861
Stranded AOCI reclassification	(1,268)
Total other comprehensive income (loss)	741	4,754	(407)
Ending Balances	(6,925)	(6,398)	(11,152)
Defined Benefit and Other Benefit Plans | Reclassification out of Accumulated Other Comprehensive Income (loss)
Summary of changes in accumulated other comprehensive income or loss by component, net of tax [Roll Forward]
Income tax expense	(74)	(856)	(533)
Net of tax	119	1,413	861
Net Prior Service Cost (Credit) | Reclassification out of Accumulated Other Comprehensive Income (loss)
Summary of changes in accumulated other comprehensive income or loss by component, net of tax [Roll Forward]
Pension and other employee benefits	(220)	674	(90)
Net Unamortized Gain (Loss) | Reclassification out of Accumulated Other Comprehensive Income (loss)
Summary of changes in accumulated other comprehensive income or loss by component, net of tax [Roll Forward]
Pension and other employee benefits	413	1,595	1,484
Accumulated Other Comprehensive Income (Loss)
Summary of changes in accumulated other comprehensive income or loss by component, net of tax [Roll Forward]
Beginning Balances	(10,754)	(10,942)	(8,785)
Other comprehensive income (loss) before reclassification	2,200	(611)	(2,788)
Amounts reclassified from accumulated other comprehensive income (loss)	51	799	631
Stranded AOCI reclassification	(1,837)
Total other comprehensive income (loss)	2,251	188	(2,157)
Ending Balances	$ (10,340)	$ (10,754)	$ (10,942)