Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 9.6	$ (140.7)	$ (25.9)	$ (342.4)
Other comprehensive income (loss), net of tax
Unrealized income on derivatives, net of income tax provision of $0.0, $0.0, $0.0 and $0.0, respectively		0.2	0.6	1.7
Employee pension and postretirement benefits, net of income tax provision of $3.3, $0.0, $4.1 and $0.0, respectively	5.7	1.1	6.8	3.5
Foreign currency translation adjustments	14.2	5.7	47.4	37.5
Net current period other comprehensive income	19.9	7.0	54.8	42.7
Comprehensive income (loss)	$ 29.5	$ (133.7)	$ 28.9	$ (299.7)