Other Comprehensive Income - Changes in Components of Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pre-tax	$ (12.4)	$ (2.5)	$ (13.4)	$ (23.4)
Tax	(1.0)	(0.1)	2.8	(1.4)
Other comprehensive (loss)	(13.4)	(2.6)	(10.6)	(24.8)
Net gain (loss) on pension and OPEB liability adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pre-tax	0.7	1.0	0.9	3.2
Tax	(0.6)	(0.2)	0.7	(0.9)
Other comprehensive (loss)	0.1	0.8	1.6	2.3
Unrealized (loss) gain on derivative instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pre-tax	(4.1)	(0.4)	(5.6)	(3.0)
Tax	1.1	0.0	1.2	1.3
Other comprehensive (loss)	(3.0)	(0.4)	(4.4)	(1.7)
Unrealized (loss) gain on foreign currency translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pre-tax	(9.0)	(3.1)	(8.7)	(23.6)
Tax	(1.5)	0.1	0.9	(1.8)
Other comprehensive (loss)	$ (10.5)	$ (3.0)	$ (7.8)	$ (25.4)