ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Components of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Before Tax
Net actuarial losses arising during the period, before tax			$ (1,042)	$ 0
Other comprehensive income (loss), before tax	$ 5,113	$ 10,112	7,928	30,171
Tax Effect
Net actuarial losses arising during the period, tax			(415)	0
Other comprehensive income, tax	2,128	3,997	3,183	11,953
Net of Tax
Net actuarial losses arising during the period, net of tax			627	0
Total other comprehensive income, net of tax	2,985	6,115	4,745	18,218
Net unrealized gains on investment securities
Before Tax
Other comprehensive income (loss) before reclassification, before tax	3,001	9,737	6,528	29,420
Reclassification from AOCI, before tax	1,640	0	1,640	0
Other comprehensive income (loss), before tax	4,641	9,737	8,168	29,420
Tax Effect
Other comprehensive income (loss) before reclassifications, tax	1,193	3,871	2,596	11,701
Reclassification from AOCI, tax	653	0	653	0
Other comprehensive income, tax	1,846	3,871	3,249	11,701
Net of Tax
Other comprehensive income (loss), before reclassifications, net of tax	1,808	5,866	3,932	17,719
Reclassification from AOCI, net of tax	(987)	0	(987)	0
Total other comprehensive income, net of tax	2,795	5,866	4,919	17,719
Amortization of net actuarial loss
Before Tax
Reclassification from AOCI, before tax	325	366	647	733
Tax Effect
Reclassification from AOCI, tax	222	124	287	248
Net of Tax
Reclassification from AOCI, net of tax	(103)	(242)	(360)	(485)
Amortization of net transition obligation
Before Tax
Reclassification from AOCI, before tax	5	4	9	8
Tax Effect
Reclassification from AOCI, tax	2	1	3	2
Net of Tax
Reclassification from AOCI, net of tax	(3)	(3)	(6)	(6)
Amortization of prior service cost
Before Tax
Reclassification from AOCI, before tax	4	5	8	10
Tax Effect
Reclassification from AOCI, tax	2	1	3	2
Net of Tax
Reclassification from AOCI, net of tax	(2)	(4)	(5)	(8)
Settlement
Before Tax
Reclassification from AOCI, before tax	138		138
Tax Effect
Reclassification from AOCI, tax	56		56
Net of Tax
Reclassification from AOCI, net of tax	(82)		(82)
Defined benefit plans, net
Before Tax
Reclassification from AOCI, before tax	472	375	(240)	751
Tax Effect
Reclassification from AOCI, tax	282	126	(66)	252
Net of Tax
Other comprehensive income (loss), before reclassifications, net of tax	0	0	(627)	0
Reclassification from AOCI, net of tax	(190)	(249)	(453)	(499)
Total other comprehensive income, net of tax	$ 190	$ 249	$ (174)	$ 499