Select Quarterly Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Sales	$ 82,287	$ 85,403	$ 85,326	$ 85,270	$ 87,906	$ 90,074	$ 93,852	$ 85,026		$ 338,286	$ 356,858	$ 317,697
Gross profit	18,695	19,431	20,537	21,259	20,979	21,393	22,347	20,489		79,922	85,208	72,662
Operating income	76	(87)	3,030	3,863	3,190	3,046	4,392	3,270		6,882	13,898	4,604
Net income	$ (656)	$ (721)	$ 1,643	$ 2,284	$ 1,628	$ 2,455	$ 2,606	$ 1,947		$ 2,550	$ 8,636	$ (222)
Earnings per share:
Basic (in dollars per share)	$ (0.04)	$ (0.04)	$ 0.1	$ 0.14	$ 0.10	$ 0.15	$ 0.16	$ 0.12	[1]	$ 0.16	$ 0.53	$ (0.01)
Diluted (in dollars per share)	$ (0.04)	$ (0.04)	$ 0.1	$ 0.14	$ 0.10	$ 0.15	$ 0.16	$ 0.12	[1]	$ 0.15	$ 0.52	$ (0.01)

[1] The ''two-class'' method was used to calculate earnings per share which resulted in the same value.