Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 28, 2019	Jun. 29, 2018	Jun. 28, 2019	Jun. 29, 2018
Income Statement [Abstract]
Net sales	$ 297,843	$ 309,085	$ 599,284	$ 612,552
Cost of sales	228,249	247,247	460,378	492,434
Gross margin	69,594	61,838	138,906	120,118
Selling, general, and administrative expense	39,891	38,473	79,955	76,935
Research and development expense	4,062	3,860	7,802	7,503
Other net	2,891	4,313	7,012	7,237
Operating profit	22,750	15,192	44,137	28,443
Interest expense—net	500	667	966	1,397
Other non-operating expense - net	3,112	437	3,357	879
Income before income taxes	19,138	14,088	39,814	26,167
Income tax expense	3,598	2,944	7,368	4,459
Net income	$ 15,540	$ 11,144	$ 32,446	$ 21,708
Basic earnings per share:
Net income per share of common stock (in dollars per share)	$ 0.76	$ 0.55	$ 1.60	$ 1.08
Diluted earnings per share:
Net income per share of common stock (in dollars per share)	$ 0.75	$ 0.54	$ 1.57	$ 1.05
Weighted-average number of shares of common stock outstanding:
Basic (in shares)	20,383	20,221	20,326	20,178
Diluted (in shares)	20,666	20,593	20,635	20,583