Equity - Reconciliation of accumulated other comprehensive loss (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Increase (Decrease) in Equity [Roll Forward]
Beginning balance			$ 643.5
Total other comprehensive income (loss), net of income tax	$ (1.4)	$ 9.3	(12.0)	$ (3.1)
Ending balance	656.2		656.2
Total other comprehensive income (loss), net of income tax	(1.4)	9.3	(12.0)	(3.1)
Ending balance	656.2		656.2
Gains and Losses on Cash Flow Hedges
Increase (Decrease) in Equity [Roll Forward]
Other comprehensive income (loss) before reclassifications	(0.1)	(0.1)	(0.1)	(0.2)
Amounts reclassified from accumulated other comprehensive income (loss)	(0.1)	0.2	(0.1)	0.3
Total other comprehensive income (loss), net of income tax	(0.2)	0.1	(0.2)	0.1
Ending balance	(0.2)	0.1	(0.2)	0.1
Other comprehensive income (loss) before reclassifications	(0.1)	(0.1)	(0.1)	(0.2)
Amounts reclassified from accumulated other comprehensive income (loss)	(0.1)	0.2	(0.1)	0.3
Total other comprehensive income (loss), net of income tax	(0.2)	0.1	(0.2)	0.1
Ending balance	(0.2)	0.1	(0.2)	0.1
Pension & Postretirement
Increase (Decrease) in Equity [Roll Forward]
Beginning balance	(48.5)	(38.7)	(47.9)	(39.9)
Other comprehensive income (loss) before reclassifications	(1.6)	0.5	(2.8)	1.0
Amounts reclassified from accumulated other comprehensive income (loss)	0.4	0.1	1.0	0.8
Total other comprehensive income (loss), net of income tax	(1.2)	0.6	(1.8)	1.8
Ending balance	(49.7)	(38.1)	(49.7)	(38.1)
Other comprehensive income (loss) before reclassifications	(1.6)	0.5	(2.8)	1.0
Amounts reclassified from accumulated other comprehensive income (loss)	0.4	0.1	1.0	0.8
Total other comprehensive income (loss), net of income tax	(1.2)	0.6	(1.8)	1.8
Ending balance	(49.7)	(38.1)	(49.7)	(38.1)
Foreign Currency Translation
Increase (Decrease) in Equity [Roll Forward]
Beginning balance	(59.6)	(94.7)	(49.6)	(81.1)
Other comprehensive income (loss) before reclassifications		8.6	(10.0)	(5.0)
Total other comprehensive income (loss), net of income tax		8.6	(10.0)	(5.0)
Ending balance	(59.6)	(86.1)	(59.6)	(86.1)
Other comprehensive income (loss) before reclassifications		8.6	(10.0)	(5.0)
Total other comprehensive income (loss), net of income tax		8.6	(10.0)	(5.0)
Ending balance	(59.6)	(86.1)	(59.6)	(86.1)
Accumulated Other Comprehensive Loss
Increase (Decrease) in Equity [Roll Forward]
Beginning balance	(108.1)	(133.4)	(97.5)	(121.0)
Other comprehensive income (loss) before reclassifications	(1.7)	9.0	(12.9)	(4.2)
Amounts reclassified from accumulated other comprehensive income (loss)	0.3	0.3	0.9	1.1
Total other comprehensive income (loss), net of income tax	(1.4)	9.3	(12.0)	(3.1)
Ending balance	(109.5)	(124.1)	(109.5)	(124.1)
Other comprehensive income (loss) before reclassifications	(1.7)	9.0	(12.9)	(4.2)
Amounts reclassified from accumulated other comprehensive income (loss)	0.3	0.3	0.9	1.1
Total other comprehensive income (loss), net of income tax	(1.4)	9.3	(12.0)	(3.1)
Ending balance	$ (109.5)	$ (124.1)	$ (109.5)	$ (124.1)