Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Unrealized derivative gain (loss), tax	$ 0.0	$ 0.0	$ 0.6
Reclassification of derivative gain (loss), tax	0.0	(0.6)	(0.6)
Total derivative gain (loss), tax	0.0	(0.6)	0.0
Unrealized actuarial gains (losses) and prior service (costs) credits, tax	0.4	0.3	0.0
Reclassifications of net actuarial and other (gain) loss and amortization of prior service cost, tax	0.0	0.0	0.0
Total pension and other postretirement benefits, tax	0.4	0.3	0.0
Other comprehensive income, tax	$ (0.4)	$ (0.3)	$ 0.0