CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net sales	$ 567,080	$ 487,076	$ 349,189
Cost of sales	458,253	399,721	286,952
Selling, general and administrative expenses	78,113	72,051	45,803
Restructuring charges	2,114	1,832	1,387
Income from operations	28,600	13,472	15,047
Interest expense	(7,588)	(3,978)	(156)
Interest income and other, net	4,720	276	274
Earnings before provision (benefit) for income taxes	25,732	9,770	15,165
Provision (benefit) for income taxes	6,535	1,167	(743)
Net earnings available to common shareholders	19,197	8,603	15,908
Class A [Member]
Net earnings available to common shareholders	$ 3,331	$ 1,492	$ 2,868
Net earnings per common share:
Common shares - basic and diluted (in dollars per share)	$ 1.53	$ 0.69	$ 1.32
Weighted-average shares outstanding:
Common shares - basic and diluted (in shares)	2,175	2,175	2,175
Dividends paid per common share:
Common shares (in dollars per share)	$ 0.24	$ 0.24	$ 0.24
Class B [Member]
Net earnings available to common shareholders	$ 15,866	$ 7,111	$ 13,040
Net earnings per common share:
Common shares - basic and diluted (in dollars per share)	$ 1.64	$ 0.75	$ 1.41
Weighted-average shares outstanding:
Common shares - basic and diluted (in shares)	9,698	9,491	9,240
Dividends paid per common share:
Common shares (in dollars per share)	$ 0.28	$ 0.28	$ 0.28