ACCUMULATED OTHER COMPREHENSIVE LOSS - Reclassification out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net gains on securities transactions	$ 0	$ 252	$ 908	$ 302
Pension and other employee benefits	1,646	1,557	3,321	3,286
Tax effect	605	1,314	1,921	2,440
Net of tax	1,621	2,577	4,328	4,853
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net of tax	232	67	(100)	260
Unrealized Gains and Losses on Securities Available for Sale [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net gains on securities transactions	0	(252)	(908)	(302)
Tax effect	0	96	343	115
Net of tax	0	(156)	(565)	(187)
Defined Benefit and Other Benefit Plans [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Tax effect	(141)	(140)	(282)	(277)
Net of tax	232	223	465	447
Prior Service Costs [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Pension and other employee benefits	(23)	(21)	(45)	(43)
Actuarial Losses [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Pension and other employee benefits	$ 396	$ 384	$ 792	$ 767