Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Net sales	$ 514,551	$ 469,333	$ 433,947
Cost of sales	358,702	349,908	330,414
Gross profit	155,849	119,425	103,533
Selling, general and administrative expenses	60,491	52,077	48,194
(Gain) loss on disposal of assets and insurance recoveries	(6,478)	337	(12)
Income from operations	101,836	67,011	55,351
Interest income, net	88	66	196
Other (expense) income, net	51	(46)	(47)
Income before taxes	101,975	67,031	55,500
Income tax provision	22,966	13,320	13,171
Net income	$ 79,009	$ 53,711	$ 42,329
Earnings per share:
Basic (usd per share)	$ 1.51	$ 1.03	$ 0.81
Diluted (usd per share)	1.49	1.02	0.80
Cash dividends declared per common share (in dollars per share)	$ 0.38	$ 0.32	$ 0.32
Weighted average shares outstanding:
Basic (in shares)	52,168,679	52,079,865	52,284,616
Diluted (in shares)	53,061,169	52,635,415	52,667,939