Accounting Policies - Income tax (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Income Taxes
Increase in unrecognized tax benefits, net	$ 2.6
Increase in unrecognized tax benefits	3.1
Increase in unrecognized tax benefits related to European tax positions	1.7
Increase in unrecognized tax benefits related to China tax positions	0.5
Increase in unrecognized tax positions related to U.S. tax positions	0.2
Reduction in unrecognized tax benefits, resulting from settlement from the completion of European audit	0.5
Amount of unrecognized tax benefits which, if recognized, would affect the effective tax rate	3.6
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance at the beginning of the period	5.1
Increases related to prior year tax positions	2.4
Decreases related to statute expirations	(0.3)
Settlements	(0.2)
Currency movement	(0.7)
Balance at the end of the period	7.7
Decrease in unrecognized tax benefits, that is reasonably possible	$ 0.5
Buildings and improvements | Minimum
Property, plant and equipment
Estimated useful lives of the assets	10 years
Buildings and improvements | Maximum
Property, plant and equipment
Estimated useful lives of the assets	40 years
Machinery and equipment | Minimum
Property, plant and equipment
Estimated useful lives of the assets	3 years
Machinery and equipment | Maximum
Property, plant and equipment
Estimated useful lives of the assets	15 years