FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
4.625 Notes
Carrying amount and estimated fair values of debt
Interest rate (as a percent)	4.625%	4.625%
4.875 Notes
Carrying amount and estimated fair values of debt
Interest rate (as a percent)	4.875%	4.875%
ABL Revolver due 2018
Carrying amount and estimated fair values of debt
Interest rate (as a percent)	3.75%
Level 2 | Term Loan
Carrying amount and estimated fair values of debt
Debt issuance costs	$ 2.0	$ 2.4
Carrying Amount | Level 1 | 4.625 Notes
Carrying amount and estimated fair values of debt
Long-term debt	688.0	688.0
Carrying Amount | Level 1 | 4.875 Notes
Carrying amount and estimated fair values of debt
Long-term debt	450.0	450.0
Carrying Amount | Level 2 | Commodity purchase contracts
Carrying amount and estimated fair values of debt
Derivative liability	1.7
Carrying Amount | Level 2 | Term Loan
Carrying amount and estimated fair values of debt
Long-term debt	193.1	194.8
Fair Value | Level 1 | 4.625 Notes
Carrying amount and estimated fair values of debt
Long-term debt	663.9	676.4
Fair Value | Level 1 | 4.875 Notes
Carrying amount and estimated fair values of debt
Long-term debt	432.8	426.9
Fair Value | Level 2 | Commodity purchase contracts
Carrying amount and estimated fair values of debt
Derivative liability	1.7
Fair Value | Level 2 | Term Loan
Carrying amount and estimated fair values of debt
Long-term debt	$ 194.2	$ 199.0