Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Unrealized income (loss) on derivatives, net of income tax benefit	$ 0.0	$ 0.0	$ 0.9
Employee pension and post retirement benefits costs, net of income tax expense (benefit)	$ 1.4	$ 4.2	$ (0.2)