Condensed Consolidated Statements of Operations and Comprehensive Income - Unaudited - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2017	Sep. 30, 2016	Sep. 29, 2017	Sep. 30, 2016
Income Statement [Abstract]
Sales	$ 363,308	$ 346,567	$ 1,071,440	$ 1,027,187
Cost of sales	265,073	248,658	782,707	741,779
Gross profit	98,235	97,909	288,733	285,408
Operating expenses:
Selling, general and administrative expenses	39,733	36,265	118,956	115,781
Research, development and engineering costs, net	13,607	11,412	39,907	42,358
Other operating expenses, net	6,264	13,370	24,955	50,004
Total operating expenses	59,604	61,047	183,818	208,143
Operating income	38,631	36,862	104,915	77,265
Interest expense, net	26,485	27,870	81,025	83,395
Other (income) loss, net	156	275	11,979	(2,772)
Income (loss) before income taxes	11,990	8,717	11,911	(3,358)
Benefit for income taxes	(1,700)	(2,741)	(430)	(1,386)
Net income (loss)	$ 13,690	$ 11,458	$ 12,341	$ (1,972)
Earnings (loss) per share:
Basic (in dollars per share)	$ 0.43	$ 0.37	$ 0.39	$ (0.06)
Diluted (in dollars per share)	$ 0.43	$ 0.37	$ 0.39	$ (0.06)
Weighted average shares outstanding:
Basic (in shares)	31,594	30,782	31,304	30,756
Diluted (in shares)	32,173	31,153	31,724	30,756
Comprehensive Income
Net income (loss)	$ 13,690	$ 11,458	$ 12,341	$ (1,972)
Foreign currency translation gain	16,728	3,191	57,863	12,250
Net change in cash flow hedges, net of tax	(339)	571	1,729	(309)
Other comprehensive income	16,389	3,762	59,592	11,941
Comprehensive income	$ 30,079	$ 15,220	$ 71,933	$ 9,969