Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 30, 2018	Mar. 31, 2017
Income Statement [Abstract]
Net sales	$ 303,467	$ 240,669
Cost of sales	245,187	197,513
Gross margin	58,280	43,156
Selling, general, and administrative expense	38,462	33,521
Research and development expense	3,643	3,130
Other net	2,924	2,818
Operating profit	13,251	3,687
Interest expense—net	730	493
Other non-operating expense - net	442	267
Income before income taxes	12,079	2,927
Income tax expense (benefit)	1,515	(123)
Net income	$ 10,564	$ 3,050
Basic earnings per share:
Net income per share of common stock (in dollars per share)	$ 0.52	$ 0.15
Diluted earnings per share:
Net income per share of common stock (in dollars per share)	0.51	0.15
Cash dividends per share (in dollars per share)	$ 0.1	$ 0.095
Weighted-average number of shares of common stock outstanding:
Basic (in shares)	20,135	19,969
Diluted (in shares)	20,574	20,375