Equity - Reconciliation of accumulated other comprehensive loss (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Increase (Decrease) in Equity [Roll Forward]
Beginning balance	$ 643.5
Total other comprehensive loss, net of income tax	(10.6)	$ (12.4)
Ending balance	633.0
Beginning balance	643.5
Total other comprehensive loss, net of income tax	(10.6)	(12.4)
Ending balance	633.0
Gains and Losses on Cash Flow Hedges
Increase (Decrease) in Equity [Roll Forward]
Other comprehensive income (loss) before reclassifications		(0.1)
Amounts reclassified from accumulated other comprehensive loss		0.1
Other comprehensive income (loss) before reclassifications		(0.1)
Amounts reclassified from accumulated other comprehensive loss		0.1
Pension & Postretirement
Increase (Decrease) in Equity [Roll Forward]
Beginning balance	(47.9)	(39.9)
Other comprehensive income (loss) before reclassifications	(1.2)	1.1
Amounts reclassified from accumulated other comprehensive loss	0.6	0.1
Total other comprehensive loss, net of income tax	(0.6)	1.2
Ending balance	(48.5)	(38.7)
Beginning balance	(47.9)	(39.9)
Other comprehensive income (loss) before reclassifications	(1.2)	1.1
Amounts reclassified from accumulated other comprehensive loss	0.6	0.1
Total other comprehensive loss, net of income tax	(0.6)	1.2
Ending balance	(48.5)	(38.7)
Foreign Currency Translation
Increase (Decrease) in Equity [Roll Forward]
Beginning balance	(49.6)	(81.1)
Other comprehensive income (loss) before reclassifications	(10.0)	(13.6)
Total other comprehensive loss, net of income tax	(10.0)	(13.6)
Ending balance	(59.6)	(94.7)
Beginning balance	(49.6)	(81.1)
Other comprehensive income (loss) before reclassifications	(10.0)	(13.6)
Total other comprehensive loss, net of income tax	(10.0)	(13.6)
Ending balance	(59.6)	(94.7)
AOCI Attributable to Parent
Increase (Decrease) in Equity [Roll Forward]
Beginning balance	(97.5)	(121.0)
Other comprehensive income (loss) before reclassifications	(11.2)	(12.6)
Amounts reclassified from accumulated other comprehensive loss	0.6	0.2
Total other comprehensive loss, net of income tax	(10.6)	(12.4)
Ending balance	(108.1)	(133.4)
Beginning balance	(97.5)	(121.0)
Other comprehensive income (loss) before reclassifications	(11.2)	(12.6)
Amounts reclassified from accumulated other comprehensive loss	0.6	0.2
Total other comprehensive loss, net of income tax	(10.6)	(12.4)
Ending balance	$ (108.1)	$ (133.4)