OTHER ASSETS (Details Textuals) - USD ($) $ in Millions		12 Months Ended
	Oct. 05, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Combination, Separately Recognized Transactions [Line Items]
Up-front payments under the ethylene agreements	$ 433.5
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Ethylene Asset	416.1
2017 Supply Contract Payment		$ 209.4
2020 Supply Contract Payment		389.2
2020 Supply Contract Payment Accretion		52.0
2020 Supply Contract Accretion Expense Recognized		3.9
Payments under long-term supply contract		$ 209.4	$ 175.7	$ 0.0
Long-term Supply Contract Weighted-average Useful Life		20 years
Amortization of Supply Contracts		$ 28.2	$ 21.5	$ 4.3
Supply Contract Amortization Expense Next Twelve Months		38.0
Supply Contract Amortization Expense, Year 2		38.0
Supply Contract Amortization Expense, Year 3		38.0
Supply Contract Amortization Expense, Year 4		62.0
Supply Contract Amortization Expense, Year 5		62.0
Minimum
Business Combination, Separately Recognized Transactions [Line Items]
Q4 2020 Supply Contract Payment		440.0
Maximum
Business Combination, Separately Recognized Transactions [Line Items]
Q4 2020 Supply Contract Payment		$ 465.0
DCP Business
Business Combination, Separately Recognized Transactions [Line Items]
Up-front payments under the ethylene agreements	$ 433.5