Business and Geographic Information - Geographical Information Attributable to Net Sales (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	$ 27,400	$ 30,000	$ 32,400	$ 28,400	$ 25,100	$ 27,000	$ 30,000	$ 29,900	$ 118,217	$ 112,035	$ 108,920
Point of destination
Revenues From External Customers And Long Lived Assets [Line Items]
Net sales									118,217	112,035	108,920
United States | Point of destination
Revenues From External Customers And Long Lived Assets [Line Items]
Net sales									108,773	103,646	98,526
Canada | Point of destination
Revenues From External Customers And Long Lived Assets [Line Items]
Net sales									6,436	5,353	7,515
Other | Point of destination
Revenues From External Customers And Long Lived Assets [Line Items]
Net sales									$ 3,008	$ 3,036	$ 2,879