Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017
Income Statement [Abstract]
Net sales	$ 309,085	$ 295,842	$ 612,552	$ 536,511
Cost of sales	247,247	241,064	492,434	438,577
Gross margin	61,838	54,778	120,118	97,934
Selling, general, and administrative expense	38,473	37,928	76,935	71,449
Research and development expense	3,860	3,544	7,503	6,674
Other net	4,313	3,204	7,237	6,022
Operating profit	15,192	10,102	28,443	13,789
Interest expense—net	667	695	1,397	1,188
Other non-operating expense - net	437	368	879	635
Income before income taxes	14,088	9,039	26,167	11,966
Income tax expense	2,944	1,726	4,459	1,603
Net income	$ 11,144	$ 7,313	$ 21,708	$ 10,363
Basic earnings per share:
Net income per share of common stock (in dollars per share)	$ 0.55	$ 0.37	$ 1.08	$ 0.52
Diluted earnings per share:
Net income per share of common stock (in dollars per share)	0.54	0.36	1.05	0.51
Cash dividends per share (in dollars per share)	$ 0.105	$ 0.1	$ 0.205	$ 0.195
Weighted-average number of shares of common stock outstanding:
Basic (in shares)	20,221	20,012	20,178	19,991
Diluted (in shares)	20,593	20,347	20,583	20,348