PENSION AND OTHER POSTRETIREMENT BENEFITS (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
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	$ 7
Effect of 1% decrease on aggregate of the service and interest cost components of net periodic benefit cost	$ 7
Temporary investment funds
Weighted-average asset allocations
Weighted-average asset allocations (as a percent)	1.00%	4.00%
Equity investment funds
Weighted-average asset allocations
Weighted-average asset allocations (as a percent)	63.00%	61.00%
Target allocation
Target allocation percentage	60.00%
Fixed income Funds
Weighted-average asset allocations
Weighted-average asset allocations (as a percent)	36.00%	35.00%
Target allocation
Target allocation percentage	40.00%
Pension Benefits
Amounts recognized in the consolidated balance sheets consist of:
Current liabilities	$ 0	$ 0
Noncurrent liabilities	(63,253)	(70,554)
Net amount recognized	(63,253)	(70,554)
Amounts recognized in accumulated other comprehensive income (loss) before taxes:
Net actuarial loss	40,493	58,780
Prior service cost (credit)	0	0
Net amount recognized	40,493	58,780
Total amount recognized in OCI
Net actuarial loss (gain)	(6,629)	48,606
Curtailment (gain)/loss	(5,413)
Amortization of:
Prior service (credit) cost	0	(10)
Actuarial (gain) loss	(6,311)	(2,006)
Gain recognized related to settlement	0	(6,060)
Gain recognized related to curtailment	0	0
Total recognized in OCI	(18,353)	$ 40,530
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	$ 500
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)	12.00%
Weighted-average asset allocations
Weighted-average asset allocations (as a percent)	100.00%
Estimated future benefit payments
2016	$ 15,906
2017	16,576
2018	16,626
2019	16,681
2020	17,938
2021 - 2025	$ 89,655
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)	6.50%
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)	6.00%
Other Benefits
Amounts recognized in the consolidated balance sheets consist of:
Current liabilities	$ (818)	$ (1,039)
Noncurrent liabilities	(5,476)	(8,765)
Net amount recognized	(6,294)	(9,804)
Amounts recognized in accumulated other comprehensive income (loss) before taxes:
Net actuarial loss	474	1,018
Prior service cost (credit)	(3,600)	(2,768)
Net amount recognized	(3,126)	(1,750)
Total amount recognized in OCI
Net actuarial loss (gain)	(687)	330
Prior service cost/(credit)	(1,684)
Amortization of:
Prior service (credit) cost	852	2,029
Actuarial (gain) loss	144	(534)
Gain recognized related to settlement	0	0
Gain recognized related to curtailment	0	(449)
Total recognized in OCI	$ (1,375)	$ 1,376
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%
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	4.50%
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	$ 137
Effect of 1% decrease on benefit obligation	130
Weighted-average asset allocations
Weighted-average asset allocations (as a percent)		100.00%
Estimated future benefit payments
Expected contributions in next fiscal year	800
2016	817
2017	784
2018	683
2019	622
2020	556
2021 - 2025	$ 2,058
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)	8.30%
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)	7.80%
Pension Plan [Member]
Estimated future benefit payments
Expected contributions in next fiscal year	$ 1,900