CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
NET INCOME (LOSS)	$ (28.7)	$ 216.7	$ (18.4)	$ 339.5
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 $1.4 for the three months ended June 30, 2017 and 2016, and $1.0 and $2.7 for the six months ended June 30, 2017 and 2016, respectively (see Notes 3 and 8).	0.8	2.5	1.7	5.0
COMPREHENSIVE INCOME (LOSS)	$ (27.9)	$ 219.2	$ (16.7)	$ 344.5