Accumulated Other Comprehensive Income (Loss) - Changes in AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	$ 179.9	$ 129.7
Stockholders' equity, ending balance	441.9	179.9
Accumulated Defined Benefit Plans Adjustment Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(108.6)	(103.8)
Other comprehensive gain (loss) before reclassification	(8.1)	(7.3)
Amounts reclassified from accumulated other comprehensive income	2.8	2.5
Stockholders' equity, ending balance	(113.9)	(108.6)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(0.1)	(0.8)
Other comprehensive gain (loss) before reclassification	0.4	(0.1)
Amounts reclassified from accumulated other comprehensive income	1.1	0.8
Stockholders' equity, ending balance	1.4	(0.1)
Accumulated Foreign Currency Adjustment Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(48.3)	(42.6)
Other comprehensive gain (loss) before reclassification	20.5	(5.7)
Amounts reclassified from accumulated other comprehensive income	0.0	0.0
Stockholders' equity, ending balance	(27.8)	(48.3)
Accumulated Other Comprehensive Income(Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(157.0)	(147.2)
Other comprehensive gain (loss) before reclassification	12.8	(13.1)
Amounts reclassified from accumulated other comprehensive income	3.9	3.3
Stockholders' equity, ending balance	$ (140.3)	$ (157.0)