Revenue Recognition - Disaggregation of Net Sales by Place of Manufacture and to Location of Customer (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Entity Wide Information Revenue From External Customer [Line Items]
Net sales	$ 484.5	$ 471.8	$ 921.0	$ 902.2
Point of origin \| Reportable Geographical Components \| Germany
Entity Wide Information Revenue From External Customer [Line Items]
Net sales	248.5	257.7	467.7	492.2
Point of origin \| Reportable Geographical Components \| United States
Entity Wide Information Revenue From External Customer [Line Items]
Net sales	289.3	208.9	534.6	405.7
Point of origin \| Reportable Geographical Components \| Canada
Entity Wide Information Revenue From External Customer [Line Items]
Net sales	95.9	82.2	174.4	153.8
Point of origin \| Reportable Geographical Components \| Belgium
Entity Wide Information Revenue From External Customer [Line Items]
Net sales	77.7	68.9	147.4	138.6
Point of origin \| Reportable Geographical Components \| Norway
Entity Wide Information Revenue From External Customer [Line Items]
Net sales	47.7	56.5	99.2	109.6
Point of origin \| Eliminations
Entity Wide Information Revenue From External Customer [Line Items]
Net sales	(274.6)	(202.4)	(502.3)	(397.7)
Point of destination \| Europe
Entity Wide Information Revenue From External Customer [Line Items]
Net sales	229.4	238.5	444.6	472.4
Point of destination \| North America
Entity Wide Information Revenue From External Customer [Line Items]
Net sales	161.5	143.6	308.3	270.6
Point of destination \| Other
Entity Wide Information Revenue From External Customer [Line Items]
Net sales	$ 93.6	$ 89.7	$ 168.1	$ 159.2