CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net reclassification adjustments for amounts recognized in net income as a component of net periodic benefit cost, tax expense	$ 0.5	$ 0.5	$ 1.2	$ 1.0
Net changes in pension and other postretirement plan assets and benefit obligations recognized in other comprehensive income, tax expense	$ 4.2	$ 0.0	$ 4.2	$ 0.0