Other Comprehensive Income - Components of Accumulated Comprehensive Income (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Accumulated pension and OPEB liability adjustments, net of income tax benefit of $13.4 million and $13.8 million at March 31, 2018 and December 31, 2017, respectively	$ (24.2)	$ (24.9)
Accumulated unrealized loss on derivative instruments, net of income tax benefit of $0.1 million and $0.2 million at March 31, 2018 and December 31, 2017, respectively	2.1	0.4
Accumulated unrealized foreign currency translation adjustments, net of income tax benefit of $3.4 million and $4.5 million at March 31, 2018 and December 31, 2017, respectively	(56.5)	(64.9)
Accumulated other comprehensive loss	(78.6)	(89.4)
Accumulated pension and OPEB tax	13.4	13.8
Accumulated tax on gain (loss) on financial instruments	0.1	0.2
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	$ 3.4	$ 4.5