PENSION AND OTHER POSTRETIREMENT BENEFITS (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effects of 1% change in assumed health care cost trend rate
Effect of 1% increase on aggregate of the service and interest cost components of net periodic benefit cost	$ 11,000
Effect of 1% decrease on aggregate of the service and interest cost components of net periodic benefit cost	10,000
Temporary investment funds
Weighted-average asset allocations
Weighted-average asset allocations (as a percent)	4.00%	4.00%
Equity investment funds
Weighted-average asset allocations
Weighted-average asset allocations (as a percent)	61.00%	63.00%
Target allocation
Target allocation percentage	60.00%
Fixed income Funds
Weighted-average asset allocations
Weighted-average asset allocations (as a percent)	35.00%	33.00%
Target allocation
Target allocation percentage	40.00%
Pension Benefits
Amounts recognized in the consolidated balance sheets consist of:
Current liabilities	0	(12,260,000)
Noncurrent liabilities	(70,554,000)	(5,152,000)
Net amount recognized	(70,554,000)	(17,412,000)
Amounts recognized in accumulated other comprehensive income before taxes:
Net actuarial loss	58,780,000	18,239,000
Prior service cost (credit)	0	11,000
Net amount recognized	58,780,000	18,250,000
Total amount recognized in OCI
Net actuarial loss (gain)	48,606,000	(53,134,000)
Amortization of:
Prior service (credit) cost	(10,000)	(14,000)
Actuarial (gain)	(2,006,000)	(8,623,000)
Loss recognized related to settlement	(6,060,000)	0
Loss recognized related to curtailment	0	0
Total recognized in OCI	40,530,000	(61,771,000)
Amount included in accumulated other comprehensive income and expected to be recognized in net periodic pension cost in next fiscal year
Estimated net actuarial loss	8,650,000
Assumptions used to determine net periodic benefit cost
Expected return on plan assets	7.10%	7.10%	7.10%
Rate of compensation increase	2.50%	2.50%	2.50%
Assumed health care cost trend rates
Annual rate of increase in the per capita cost of covered prescription drug benefits (as a percent)	7.00%
Weighted-average asset allocations
Weighted-average asset allocations (as a percent)	100.00%
Estimated future benefit payments
2015	7,699,000
2016	8,958,000
2017	10,342,000
2018	11,678,000
2019	12,978,000
2020 - 2024	84,889,000
Pension Benefits | Maximum
Assumptions used to determine net periodic benefit cost
Discount rate	4.27%	5.18%
Assumed health care cost trend rates
Annual rate of increase in the per capita cost of covered health care benefits (as a percent)	8.25%
Pension Benefits | Minimum
Assumptions used to determine net periodic benefit cost
Discount rate	4.20%	5.10%
Assumed health care cost trend rates
Annual rate of increase in the per capita cost of covered health care benefits (as a percent)	7.75%
Other Benefits
Amounts recognized in the consolidated balance sheets consist of:
Current liabilities	(1,039,000)	(1,155,000)
Noncurrent liabilities	(8,765,000)	(8,908,000)
Net amount recognized	(9,804,000)	(10,063,000)
Amounts recognized in accumulated other comprehensive income before taxes:
Net actuarial loss	1,018,000	1,913,000
Prior service cost (credit)	(2,768,000)	(5,040,000)
Net amount recognized	(1,750,000)	(3,127,000)
Total amount recognized in OCI
Net actuarial loss (gain)	330,000	(583,000)
Amortization of:
Prior service (credit) cost	2,029,000	3,378,000
Actuarial (gain)	(534,000)	(767,000)
Loss recognized related to settlement	0	0
Loss recognized related to curtailment	(449,000)	0
Total recognized in OCI	1,376,000	2,028,000
Assumed health care cost trend rates
Annual rate of increase in the per capita cost of covered prescription drug benefits (as a percent)	7.25%
For covered prescription drug benefits, the ultimate rate to which the rate is assumed to decrease for 2017 and thereafter (2013 assumption) and for 2019 and thereafter (2012 assumption), as a percent	5.00%
For covered health care benefits, the ultimate rate to which the rate is assumed to decrease for 2019 and thereafter (2013 assumption) and for 2018 and thereafter (2012 assumption), as a percent	5.00%
Effects of 1% change in assumed health care cost trend rate
Effect of 1% increase on benefit obligation	343,000
Effect of 1% decrease on benefit obligation	336,000
Weighted-average asset allocations
Weighted-average asset allocations (as a percent)		100.00%
Estimated future benefit payments
Expected contributions in next fiscal year	1,000,000
2015	1,038,000
2016	1,023,000
2017	940,000
2018	851,000
2019	823,000
2020 - 2024	$ 3,332,000
Other Benefits | Maximum
Assumptions used to determine net periodic benefit cost
Discount rate	4.20%	5.05%
Assumed health care cost trend rates
Annual rate of increase in the per capita cost of covered health care benefits (as a percent)	9.00%
Other Benefits | Minimum
Assumptions used to determine net periodic benefit cost
Discount rate	3.03%	2.98%
Assumed health care cost trend rates
Annual rate of increase in the per capita cost of covered health care benefits (as a percent)	10.00%