BENEFIT PLANS, Benefits (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation for defined benefit pension plan prior to plan revaluation	$ 116,400,000	$ 99,600,000
Accumulated other comprehensive income (loss), negative postretirement medical plan amendment, arising during period, net of tax				3,500,000
Amounts recognized in AOCI, net of tax [Abstract]
Total	9,571,000	(20,640,000)	2,911,000
Prior service costs [Abstract]
Maximum percentage of net gain or loss over the greater of the projected benefit obligation or the market-related value of assets without requiring amortization (hundredths)	10.00%
Pension Benefits [Member]
Amounts recognized in AOCI, net of tax [Abstract]
Prior service cost	932,000	(46,000)
Net (gain) loss	8,492,000	(20,513,000)
Total	9,424,000	(20,559,000)
Costs that will be amortized from accumulated other comprehensive income (loss) in net periodic (income) cost in next fiscal year [Abstract]
Prior service cost	9,000
Net loss	1,447,000
Total	1,456,000
Weighed average assumption used in calculating benefit obligations [Abstract]
Discount rate (in hundredths)	4.50%	5.00%
Expected return on plan assets (in hundredths)	7.00%	7.00%
Rate of compensation increase (in hundredths)	3.50%	3.50%
Net periodic benefit cost [Abstract]
Service cost	3,530,000	3,988,000	3,392,000
Interest cost	5,271,000	4,120,000	4,393,000
Expected return on plan assets	(11,922,000)	(10,149,000)	(9,196,000)
Amortization of unrecognized net (gain) loss	(307,000)	4,028,000	3,687,000
Amortization of prior service cost	5,000	75,000	(147,000)
Net periodic benefit cost	(3,423,000)	2,062,000	2,129,000
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate (in hundredths)	5.00%	3.40%	4.10%
Expected return on plan assets (in hundredths)	7.00%	7.00%	7.50%
Rate of compensation increase (in hundredths)	3.50%	3.50%	4.00%
Post-retirement Benefits [Member]
Amounts recognized in AOCI, net of tax [Abstract]
Prior service cost	109,000	109,000
Net (gain) loss	38,000	(190,000)
Total	147,000	(81,000)
Costs that will be amortized from accumulated other comprehensive income (loss) in net periodic (income) cost in next fiscal year [Abstract]
Prior service cost	(179,000)
Net loss	5,000
Total	(174,000)
Weighed average assumption used in calculating benefit obligations [Abstract]
Discount rate (in hundredths)	4.50%	4.80%
Net periodic benefit cost [Abstract]
Service cost	0	0	0
Interest cost	102,000	88,000	114,000
Expected return on plan assets	0	0	0
Amortization of unrecognized net (gain) loss	(7,000)	12,000	11,000
Amortization of prior service cost	(179,000)	(179,000)	(822,000)
Net periodic benefit cost	$ (84,000)	$ (79,000)	$ (697,000)
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate (in hundredths)	4.80%	3.20%	3.90%