CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net sales	$ 146,489	$ 126,386	$ 405,451	$ 371,671
Cost of sales	117,282	98,686	326,096	291,481
Gross profit	29,207	27,700	79,355	80,190
Selling, general and administrative expenses	18,691	20,906	57,690	63,604
Restructuring charges	17	0	62	171
Income from operations	10,499	6,794	21,603	16,415
Interest expense	(1,391)	(1,466)	(3,917)	(4,476)
Interest income and other, net	43	(244)	(479)	(720)
Earnings before provision for income taxes	9,151	5,084	17,207	11,219
(Benefit from) provision for income taxes	(2,201)	60	523	2,329
Net earnings available to common stockholders	11,352	5,024	16,684	8,890
Class A Common Share [Member]
Net earnings available to common stockholders	$ 1,942	$ 860	$ 2,852	$ 1,507
Net earnings per common share:
Common share - basic and diluted (in dollars per share)	$ 0.89	$ 0.40	$ 1.31	$ 0.69
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	$ 0.18	$ 0.18
Class B Common Share [Member]
Net earnings available to common stockholders	$ 9,410	$ 4,164	$ 13,832	$ 7,383
Net earnings per common share:
Common share - basic and diluted (in dollars per share)	$ 0.94	$ 0.42	$ 1.40	$ 0.75
Weighted-average number of shares outstanding:
Common share - basic and diluted (in shares)	9,972	9,864	9,891	9,856
Dividends paid per common share:
Common share (in dollars per share)	$ 0.07	$ 0.07	$ 0.21	$ 0.21