Condensed Consolidated Statements of Operations and Comprehensive Income - Unaudited - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jul. 01, 2016	Jun. 30, 2017	Jul. 01, 2016
Income Statement [Abstract]
Sales	$ 362,719	$ 348,382	$ 708,132	$ 680,620
Cost of sales	263,447	252,351	517,634	493,121
Gross profit	99,272	96,031	190,498	187,499
Operating expenses:
Selling, general and administrative expenses	39,724	37,628	79,223	79,516
Research, development and engineering costs, net	12,889	13,640	26,300	30,946
Other operating expenses, net	6,920	15,494	18,691	36,634
Total operating expenses	59,533	66,762	124,214	147,096
Operating income	39,739	29,269	66,284	40,403
Interest expense, net	25,647	27,908	54,540	55,525
Other (income) loss, net	9,976	674	11,823	(3,047)
Income (loss) before provision for income taxes	4,116	687	(79)	(12,075)
Provision for income taxes	1,126	1,457	1,270	1,355
Net income (loss)	$ 2,990	$ (770)	$ (1,349)	$ (13,430)
Earnings (loss) per share:
Basic (in dollars per share)	$ 0.10	$ (0.03)	$ (0.04)	$ (0.44)
Diluted (in dollars per share)	$ 0.09	$ (0.03)	$ (0.04)	$ (0.44)
Weighted average shares outstanding:
Basic (in shares)	31,302	30,767	31,159	30,743
Diluted (in shares)	31,982	30,767	31,159	30,743
Comprehensive Income (Loss)
Net income (loss)	$ 2,990	$ (770)	$ (1,349)	$ (13,430)
Foreign currency translation gain (loss)	34,599	(9,701)	41,135	9,059
Net change in cash flow hedges, net of tax	318	(1,247)	2,068	(880)
Other comprehensive income (loss)	34,917	(10,948)	43,203	8,179
Comprehensive income (loss)	$ 37,907	$ (11,718)	$ 41,854	$ (5,251)