Business and Geographic Segments - Net Property and Equipment by Segment (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net property and equipment:
Net property and equipment	$ 588.7	$ 516.0	$ 515.6
United States
Net property and equipment:
Net property and equipment	80.8	76.2	77.0
Germany
Net property and equipment:
Net property and equipment	259.2	223.7	229.9
Canada
Net property and equipment:
Net property and equipment	69.0	60.5	55.0
Norway
Net property and equipment:
Net property and equipment	81.7	75.5	71.9
Belgium
Net property and equipment:
Net property and equipment	$ 98.0	$ 80.1	$ 81.8