Business and Geographic Segments - Net Sales by Point of Origin and Point of Destination (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net sales	$ 495.9	$ 496.5	$ 481.7	$ 405.3	$ 390.5	$ 393.1	$ 387.5	$ 348.3	$ 1,879.4	$ 1,519.4	$ 1,487.9
Point Of Origin
Segment Reporting Information [Line Items]
Net sales									1,879.4	1,519.4	1,487.9
Point Of Destination
Segment Reporting Information [Line Items]
Net sales									1,879.4	1,519.4	1,487.9
United States | Point Of Origin
Segment Reporting Information [Line Items]
Net sales									992.3	819.3	796.9
Germany | Point Of Origin
Segment Reporting Information [Line Items]
Net sales									918.6	699.8	690.0
Canada | Point Of Origin
Segment Reporting Information [Line Items]
Net sales									309.2	257.7	216.9
Belgium | Point Of Origin
Segment Reporting Information [Line Items]
Net sales									279.9	187.4	198.8
Norway | Point Of Origin
Segment Reporting Information [Line Items]
Net sales									216.4	164.8	183.5
North America | Point Of Destination
Segment Reporting Information [Line Items]
Net sales									668.3	566.8	559.0
Europe | Point Of Destination
Segment Reporting Information [Line Items]
Net sales									899.2	698.2	700.9
Asia and other | Point Of Destination
Segment Reporting Information [Line Items]
Net sales									311.9	254.4	228.0
Geography Eliminations | Point Of Origin
Segment Reporting Information [Line Items]
Net sales									$ (837.0)	$ (609.6)	$ (598.2)