Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Net sales	$ 543,494	$ 465,771
Cost of sales	409,111	346,041
Gross profit	134,383	119,730
Research and development costs	21,891	23,611
Selling, general and administrative expenses	86,612	78,704
Restructuring charges	1,201	601
Gains on sales of property	(6,578)	(1,853)
Income from operations	31,257	18,667
Interest expense	(3,542)	(4,746)
Other expense, net	(388)	(1,785)
Earnings before provision for (benefit from) income taxes	27,327	12,136
Provision for (benefit from) income taxes	2,506	(659)
Net earnings available to common shareholders	24,821	12,795
Common Class A [Member]
Net earnings available to common shareholders	$ 4,076	$ 2,089
Net earnings per common share:
Common shares - basic and diluted (in dollars per share)	$ 1.90	$ 0.97
Weighted-average shares outstanding:
Common shares - basic and diluted (in shares)	2,145	2,145
Common Class B [Member]
Net earnings available to common shareholders	$ 20,745	$ 10,706
Net earnings per common share:
Common shares - basic and diluted (in dollars per share)	$ 2.02	$ 1.05
Weighted-average shares outstanding:
Common shares - basic and diluted (in shares)	10,258	10,185