CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2018	Sep. 29, 2017	Sep. 28, 2018	Sep. 29, 2017
Income Statement [Abstract]
Net sales	$ 361,496	$ 325,076	$ 1,050,553	$ 944,422
Cost of sales	269,503	244,171	785,798	707,017
Gross profit	91,993	80,905	264,755	237,405
Operating expenses	81,725	70,411	233,799	211,627
Operating income	10,268	10,494	30,956	25,778
Interest expense	4,676	5,593	15,036	17,406
Loss on asset disposal	0	10	30	10
Income before income taxes	5,592	4,891	15,890	8,362
Provision for income tax expense	1,435	2,040	4,370	3,479
Net income	4,157	2,851	11,520	4,883
Other comprehensive income (loss):
Foreign currency translation adjustments	(96)	369	(1,299)	605
Comprehensive income	$ 4,061	$ 3,220	$ 10,221	$ 5,488
Net income per share:
Basic (in dollars per share)	$ 0.14	$ 0.11	$ 0.40	$ 0.19
Diluted (in dollars per share)	$ 0.14	$ 0.11	$ 0.40	$ 0.19
Weighted average common shares outstanding:
Basic (in shares)	29,080,929	26,092,387	28,458,972	26,011,913
Diluted (in shares)	29,743,851	27,387,619	29,619,703	26,063,655