Stockholders' Equity - Reconciliation of accumulated other comprehensive income (loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Increase (Decrease) in Equity [Roll Forward]
Beginning balance			$ 601.3
Total other comprehensive loss, net of income tax	$ (14.8)	$ (1.6)	(14.4)	$ (18.9)
Ending balance	625.1		625.1
Gains and Losses on Cash Flow Hedges
Increase (Decrease) in Equity [Roll Forward]
Beginning balance	0.4	(3.2)	(0.3)	0.1
Other comprehensive income (loss) before reclassifications	(2.2)	(1.2)	(3.0)	(4.8)
Amounts reclassified from accumulated other comprehensive loss	0.9	2.5	2.4	2.8
Total other comprehensive loss, net of income tax	(1.3)	1.3	(0.6)	(2.0)
Ending balance	(0.9)	(1.9)	(0.9)	(1.9)
Pension & Postretirement
Increase (Decrease) in Equity [Roll Forward]
Beginning balance	(35.2)	(43.7)	(36.2)	(45.1)
Other comprehensive income (loss) before reclassifications		(0.2)	0.2	(0.2)
Amounts reclassified from accumulated other comprehensive loss	0.4	4.4	1.2	5.8
Total other comprehensive loss, net of income tax	0.4	4.2	1.4	5.6
Ending balance	(34.8)	(39.5)	(34.8)	(39.5)
Foreign Currency Translation
Increase (Decrease) in Equity [Roll Forward]
Beginning balance	(81.4)	(67.8)	(80.1)	(52.4)
Other comprehensive income (loss) before reclassifications	(13.9)	(7.1)	(15.2)	(22.5)
Total other comprehensive loss, net of income tax	(13.9)	(7.1)	(15.2)	(22.5)
Ending balance	(95.3)	(74.9)	(95.3)	(74.9)
Accumulated Other Comprehensive Loss
Increase (Decrease) in Equity [Roll Forward]
Beginning balance	(116.2)	(114.7)	(116.6)	(97.4)
Other comprehensive income (loss) before reclassifications	(16.1)	(8.5)	(18.0)	(27.5)
Amounts reclassified from accumulated other comprehensive loss	1.3	6.9	3.6	8.6
Total other comprehensive loss, net of income tax	(14.8)	(1.6)	(14.4)	(18.9)
Ending balance	$ (131.0)	$ (116.3)	$ (131.0)	$ (116.3)