CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
NET INCOME (LOSS)	$ (20.9)	$ 5.5	$ (39.3)	$ 345.0
Net changes in pension and other postretirement plan assets and benefit obligations recognized in other comprehensive income, net of income tax expense of $10.3 for the three and nine months ended September 30, 2016 (See Note 3).	0.0	19.2	0.0	19.2
OTHER COMPREHENSIVE INCOME:
Net reclassification adjustment for amounts recognized in net income (loss) as a component of net periodic benefit cost, net of income tax expense of $0.5 and $0.5 for the three months ended September 30, 2017 and 2016 and $1.5 and $3.2 for the nine months ended September 30, 2017 and 2016, respectively (see Notes 3 and 8).	1.0	1.0	2.7	6.0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	1.0	20.2	2.7	25.2
COMPREHENSIVE INCOME (LOSS)	$ (19.9)	$ 25.7	$ (36.6)	$ 370.2