Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Income Statement [Abstract]
Net sales	$ 301,441	$ 303,467
Cost of sales	232,129	245,187
Gross margin	69,312	58,280
Selling, general, and administrative expense	40,064	38,462
Research and development expense	3,740	3,643
Other net	4,121	2,924
Operating profit	21,387	13,251
Interest expense—net	466	730
Other non-operating expense - net	245	442
Income before income taxes	20,676	12,079
Income tax expense	3,770	1,515
Net income	$ 16,906	$ 10,564
Basic earnings per share:
Net income per share of common stock (in dollars per share)	$ 0.83	$ 0.52
Diluted earnings per share:
Net income per share of common stock (in dollars per share)	$ 0.82	$ 0.51
Weighted-average number of shares of common stock outstanding:
Basic (in shares)	20,267	20,135
Diluted (in shares)	20,606	20,574