Segment and Geographic Information - Schedule of Net Sales to External Customers and Location of Net Plant, Equipment and Timberlands (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 229,480	$ 209,855	$ 215,742	$ 211,209	$ 209,327	$ 210,120	$ 195,974	$ 184,941	$ 866,286	$ 800,362	$ 761,216
Plant, Equipment and Timberlands – Net	556,044				515,183				556,044	515,183	428,772
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									124,690	89,773	74,986
Plant, Equipment and Timberlands – Net	109,797				105,663				109,797	105,663	44,851
Germany [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									483,628	450,668	427,520
Plant, Equipment and Timberlands – Net	286,839				240,932				286,839	240,932	220,380
United Kingdom [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									76,053	76,594	78,759
Plant, Equipment and Timberlands – Net	50,483				55,494				50,483	55,494	51,903
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									114,877	120,433	115,901
Plant, Equipment and Timberlands – Net	74,448				78,220				74,448	78,220	79,727
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									67,038	62,894	64,050
Plant, Equipment and Timberlands – Net	$ 34,477				$ 34,874				$ 34,477	$ 34,874	$ 31,911