COMMITMENTS AND CONTINGENCIES (Narrative) (Details) $ in Thousands	1 Months Ended	12 Months Ended
	May. 31, 2007 entity mi	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Commitments And Contingencies Disclosure [Line Items]
Expenditures under the noncapital purchase commitments		$ 76,178	$ 65,582	$ 83,699
Commitments of minimum royalties under mineral leases		217,380
Expenditures for mineral royalties under mineral leases		58,048	49,685	53,768
Unrecognized tax benefits		8,447	$ 7,057	$ 12,155	$ 13,550
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
Texas Brine and Occidental Chemical Co [Member]
Commitments And Contingencies Disclosure [Line Items]
Total amount of damages claimed		500,000
Cooperating Parties Group [Member]
Commitments And Contingencies Disclosure [Line Items]
Estimated operation and maintenance costs		$ 93,000
Estimated operation and maintenance costs, Period		30 years
Minimum [Member] | EPA [Member]
Commitments And Contingencies Disclosure [Line Items]
Estimated implementation costs		$ 950,000
Minimum [Member] | Cooperating Parties Group [Member]
Commitments And Contingencies Disclosure [Line Items]
Estimated implementation costs		475,000
Maximum [Member] | EPA [Member]
Commitments And Contingencies Disclosure [Line Items]
Estimated implementation costs		1,730,000
Maximum [Member] | Cooperating Parties Group [Member]
Commitments And Contingencies Disclosure [Line Items]
Estimated implementation costs		725,000
Standby Letters of Credit [Member]
Commitments And Contingencies Disclosure [Line Items]
Other Liabilities		38,864
Property, Plant and Equipment [Member]
Commitments And Contingencies Disclosure [Line Items]
Unconditional purchase obligations		146,864
Noncapital [Member]
Commitments And Contingencies Disclosure [Line Items]
Unconditional purchase obligations		$ 48,602