COMMITMENTS AND CONTINGENCIES (Narrative) (Details)	1 Months Ended	12 Months Ended
	May 31, 2007 entity mi	Dec. 31, 2016 USD ($) item	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Loss Contingencies [Line Items]
Expenditures under the noncapital purchase commitments		$ 60,591,000	$ 76,178,000	$ 65,582,000
Commitments of minimum royalties under mineral leases		216,241,000
Expenditures for mineral royalties under mineral leases		62,978,000	58,048,000	49,685,000
Asset retirement obligations		223,872,000	226,594,000	226,565,000
Unrecognized tax benefits		10,828,000	$ 8,447,000	$ 7,057,000	$ 12,155,000
Number of other companies to perform a Remedial Investigation/ Feasibility Study related to the Lower Passaic River Clean-Up lawsuit | entity	70
Number of miles of the River used in the Remedial Investigation/Feasibility Study | mi	17
Minimum [Member] | Texas Brine and Occidental Chemical Co [Member]
Loss Contingencies [Line Items]
Total amount of damages claimed		500,000,000
Maximum [Member] | EPA [Member]
Loss Contingencies [Line Items]
Estimated implementation costs		1,380,000,000
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Outstanding standby letters of credit		39,538,000
Property, Plant and Equipment [Member]
Loss Contingencies [Line Items]
Unconditional purchase obligations		132,046,000
Recorded unconditional purchase obligation in 2017		$ 131,846,000
Number of self-unloading ships | item		2
Property, Plant and Equipment [Member] | Ship Construction [Member]
Loss Contingencies [Line Items]
Recorded unconditional purchase obligation in 2017		$ 85,293,000
Noncapital [Member]
Loss Contingencies [Line Items]
Unconditional purchase obligations		55,037,000
Recorded unconditional purchase obligation in 2017		$ 24,402,000