OTHER ASSETS (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Oct. 05, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Other Assets [Abstract]
Investments in non-consolidated affiliates		$ 28.2	$ 26.1	$ 28.2	$ 26.1	$ 26.7
Deferred debt issuance costs		2.7	2.8	2.7	2.8	2.6
Tax-Related Receivable, Noncurrent		13.1	15.8	13.1	15.8	17.5
Interest rate swaps		3.7	2.5	3.7	2.5	7.7
Supply Contracts		1,146.3	572.8	1,146.3	572.8	566.7
Other		21.6	20.3	21.6	20.3	23.2
Other assets		1,215.6	640.3	1,215.6	640.3	$ 644.4
Business Combination, Separately Recognized Transactions [Line Items]
2020 Supply Contract Payment		389.2
2020 Supply Contract Payment Accretion		51.0		51.0
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Ethylene Asset	$ 416.1
2017 Supply Contract Payment		209.4
Payments under long-term supply contracts				(209.4)	(175.7)
Amortization of Supply Contracts		$ 6.3	$ 6.0	18.9	$ 14.7
Minimum
Business Combination, Separately Recognized Transactions [Line Items]
2020 Supply Contract Payment				440.0
Maximum
Business Combination, Separately Recognized Transactions [Line Items]
2020 Supply Contract Payment				$ 465.0
Blue Cube Business
Business Combination, Separately Recognized Transactions [Line Items]
Payments for Supply of Ethylene	$ 433.5