Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Revenue	$ 1,136,256	$ 1,090,704	$ 1,029,353
Cost of goods sold	857,921	827,156	789,159
Gross profit	278,335	263,548	240,194
Operating expenses:
Selling, general and administrative expenses	225,738	209,967	197,291
Depreciation and amortization	13,390	17,916	17,472
Change in fair value of contingent consideration	677	10,417	(270)
Goodwill impairment charge	0	0	37,539
Intangible asset impairment charges	0	70
Restructuring charges	0	5,615	1,053
Income (loss) from operations	38,530	19,563	(13,093)
Other income (expense):
Interest income	97	86	69
Interest expense	(4,729)	(4,171)	(4,612)
Other, net	(1,788)	(153)	(3,135)
Total other expense	(6,420)	(4,238)	(7,678)
Income (loss) before taxes	32,110	15,325	(20,771)
Income tax expense	13,131	10,955	12,292
Net income (loss)	$ 18,979	$ 4,370	$ (33,063)
Basic earnings (loss) per share (in USD per share)	$ 0.35	$ 0.08	$ (0.63)
Diluted earnings (loss) per share (in USD per share)	$ 0.35	$ 0.08	$ (0.63)