CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net sales	$ 140,710	$ 131,617	$ 258,961	$ 245,285
Cost of sales	111,696	102,490	208,814	192,795
Gross profit	29,014	29,127	50,147	52,490
Selling, general and administrative expenses	18,306	21,723	38,998	42,698
Restructuring charges	41	138	45	171
Income from operations	10,667	7,266	11,104	9,621
Interest expense	(1,349)	(1,586)	(2,527)	(3,010)
Interest income and other, net	(285)	(268)	(521)	(476)
Earnings before provision for income taxes	9,033	5,412	8,056	6,135
Provision for income taxes	2,399	2,292	2,724	2,269
Net earnings available to common stockholders	6,634	3,120	5,332	3,866
Class A Common Share [Member]
Net earnings available to common stockholders	$ 1,141	$ 530	$ 901	$ 646
Net earnings per common share:
Common share - basic and diluted (in dollars per share)	$ 0.52	$ 0.24	$ 0.41	$ 0.30
Weighted-average number of shares outstanding:
Common share - basic and diluted (in shares)	2,175	2,175	2,175	2,175
Dividends paid per common share:
Common share (in dollars per share)	$ 0.06	$ 0.06	$ 0.12	$ 0.12
Class B Common Share [Member]
Net earnings available to common stockholders	$ 5,493	$ 2,590	$ 4,431	$ 3,220
Net earnings per common share:
Common share - basic and diluted (in dollars per share)	$ 0.56	$ 0.26	$ 0.45	$ 0.33
Weighted-average number of shares outstanding:
Common share - basic and diluted (in shares)	9,844	9,859	9,850	9,852
Dividends paid per common share:
Common share (in dollars per share)	$ 0.07	$ 0.07	$ 0.14	$ 0.14