Quarterly Results of Operations (Unaudited) - Quarterly Results of Operations (Detail) - 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]
Net sales	$ 29,600	$ 29,700	$ 33,700	$ 31,200	$ 27,400	$ 30,000	$ 32,400	$ 28,400	$ 124,243	$ 118,217	$ 112,035
Gross margin	9,000	9,500	10,900	9,600	7,900	9,600	11,200	9,500	38,963	38,271	34,825
Operating income	3,500	4,300	5,600	4,300	2,900	4,500	6,000	4,400	17,666	17,811	15,235
Net income	$ 3,200	$ 3,900	$ 4,900	$ 4,000	$ 2,700	$ 3,900	$ 5,000	$ 3,700	$ 15,998	$ 15,325	$ 13,203
Basic and diluted earnings per share	$ 0.26	$ 0.31	$ 0.39	$ 0.32	$ 0.22	$ 0.32	$ 0.40	$ 0.30	$ 1.29	$ 1.23	$ 1.06

The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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