Geographic Information - Geographical Information Attributable to Net Sales (Detail) - USD ($) $ in Thousands	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
Revenues From External Customers And Long Lived Assets [Line Items]
Net sales	$ 25,100	$ 27,000	$ 30,000	$ 29,900	$ 26,300	$ 28,400	$ 27,100	$ 27,100	$ 112,035	$ 108,920	$ 108,994
Point of destination
Revenues From External Customers And Long Lived Assets [Line Items]
Net sales									112,035	108,920	108,994
United States | Point of destination
Revenues From External Customers And Long Lived Assets [Line Items]
Net sales									103,646	98,526	103,737
Canada | Point of destination
Revenues From External Customers And Long Lived Assets [Line Items]
Net sales									5,353	7,515	2,352
Other | Point of destination
Revenues From External Customers And Long Lived Assets [Line Items]
Net sales									$ 3,036	$ 2,879	$ 2,905