FAIR VALUE MEASUREMENTS - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Assets:
Derivatives assets	$ 2.4	$ 0.1
Liabilities:
Derivative liabilities		0.1
Fair Value, Measurements, Recurring
Assets:
Total assets	2.4	0.1
Liabilities:
Total liabilities		0.1
Fair Value, Measurements, Recurring | Commodity
Assets:
Derivatives assets	2.4	0.1
Liabilities:
Derivative liabilities		0.1
Fair Value, Measurements, Recurring | Level 1
Assets:
Total assets	0.0	0.0
Liabilities:
Total liabilities		0.0
Fair Value, Measurements, Recurring | Level 1 | Commodity
Assets:
Derivatives assets	0.0	0.0
Liabilities:
Derivative liabilities		0.0
Fair Value, Measurements, Recurring | Level 2
Assets:
Total assets	0.0	0.1
Liabilities:
Total liabilities		0.1
Fair Value, Measurements, Recurring | Level 2 | Commodity
Assets:
Derivatives assets	0.0	0.1
Liabilities:
Derivative liabilities		0.1
Fair Value, Measurements, Recurring | Level 3
Assets:
Derivatives assets	2.4
Total assets	2.4	0.0
Liabilities:
Total liabilities		0.0
Fair Value, Measurements, Recurring | Level 3 | Commodity
Assets:
Derivatives assets	$ 2.4	0.0
Liabilities:
Derivative liabilities		$ 0.0