BENEFIT PLANS (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) employee ShareBasedCompensationPlan item	Dec. 31, 2016 USD ($) item	Dec. 31, 2015 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Number Of Defined Contribution Plans | ShareBasedCompensationPlan	2
Expected return on plan assets	7.00%
Contributions to multiemployer pension plans	$ 9,253	$ 10,435	$ 9,800
Percentage of contributions to individual multiemployer pension funds	5.00%	5.00%	5.00%
Percentage of domestic hourly labor force covered by collective bargaining agreements	12.40%
Percentage of domestic hourly labor force covered by collective bargaining agreements expiring in 2017	4.30%
Number of unfunded supplemental retirement plans | item	1	1
Accrued costs for supplemental retirement plan	$ 1,252	$ 1,320
Amount plan assets of Chemical Plan exceeds accumulated benefit obligation	5,346	277
Expense recognized related to defined contribution plans	$ 44,562	45,295	$ 36,085
Mexico [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of employees | employee	310
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of funded, noncontributory defined benefit pension plans | ShareBasedCompensationPlan	3
Normal retirement age	65 years
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements	$ 0	0	(2,031)
Projected benefit obligation	1,091,223	1,006,674	$ 988,453
Accumulated benefit obligation	1,090,482	$ 1,006,001
Estimated net actuarial loss expected to be amortized from accumulated other comprehensive income	9,782
Estimated prior service cost that will be amortized from accumulated other comprehensive income	$ 1,339
Expected return on plan assets	7.00%	7.50%	7.50%
Employer contributions	$ 20,023	$ 9,576	$ 14,047
Estimated employer contribution in 2018	$ 109,477
Discount rate	3.72%	4.29%	4.54%
Estimated weighted-average discount rate to measure service cost	4.63%	4.68%
Estimated weighted-average discount rate to measure interest cost	3.63%	3.79%
Pension Benefits [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discretionary qualified plan contribution	$ 10,600
Employer contributions		$ 0	$ 0
Estimated employer contribution in 2018	$ 100,000
Pension Benefits [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of unfunded, nonqualified pension plans | ShareBasedCompensationPlan	3
Projected benefit obligation	$ 82,136	85,021
Accumulated benefit obligation	82,136	85,021
Employer contributions	9,423	9,576	14,047
Estimated employer contribution in 2018	$ 9,477
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Normal retirement age	65 years
Projected benefit obligation	$ 43,480	$ 45,546	$ 48,605
Estimated net actuarial loss expected to be amortized from accumulated other comprehensive income	(1,525)
Estimated prior service cost that will be amortized from accumulated other comprehensive income	(3,962)
Estimated employer contribution in 2018	$ 5,624
Discount rate	3.33%	3.58%	3.69%
Estimated weighted-average discount rate to measure service cost	3.96%	3.77%
Estimated weighted-average discount rate to measure interest cost	2.89%	2.81%
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.24%	3.43%
Minimum [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation ranges for plan assets	50.00%
Minimum [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation ranges for plan assets	15.00%
Minimum [Member] | Specialty Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation ranges for plan assets	0.00%
Minimum [Member] | Commodities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation ranges for plan assets	0.00%
Minimum [Member] | Cash Reserves [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation ranges for plan assets	0.00%
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.79%	4.41%
Maximum [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation ranges for plan assets	77.00%
Maximum [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation ranges for plan assets	27.00%
Maximum [Member] | Specialty Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation ranges for plan assets	20.00%
Maximum [Member] | Commodities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation ranges for plan assets	6.00%
Maximum [Member] | Cash Reserves [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation ranges for plan assets	5.00%