Property, Plant and Equipment - Schedule of Property,Plant and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property Plant And Equipment [Line Items]
Cost	$ 159,405	$ 149,572
Accumulated depreciation	(107,099)	(101,023)
Total	52,306	48,549
Buildings [Member]
Property Plant And Equipment [Line Items]
Cost	3,328	3,683
Plant equipment and instrumentation [Member]
Property Plant And Equipment [Line Items]
Cost	150,366	140,110
Furniture and fixtures [Member]
Property Plant And Equipment [Line Items]
Cost	$ 5,711	$ 5,779