Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Noncontrolling Interest [Member]
Balance at Dec. 31, 2016	$ 369,413	$ 300,426	$ 25,522	$ 53,838	$ (13,104)	$ 2,731
Balance, shares at Dec. 31, 2016		85,744
Employee Stock Purchase Plan, Value	281	$ 281	0	0	0	0
Employee Stock Purchase Plan, Shares		40
Exercise of options	4,400	$ 7,612	(3,212)	0	0	0
Exercise of options, shares		889
Dividends Preferred Stock Cash	(5,100)	$ 0	0	(5,100)	0	0
Preferred Stock Accretion To Redemption Value1	(748)	0	0	(748)	0	0
Stock based compensation	4,133	0	4,133	0	0	0
Earnings (loss)	(17,169)	0	0	(17,833)	0	664
Currency translation adjustment	4,954	0	0	0	5,001	(47)
Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax	257	0	0	0	257	0
Minority Interest Decrease From Redemptions	(1,737)	0	214	0	(82)	(1,869)
Balance at Sep. 30, 2017	358,684	$ 308,319	26,657	30,157	(7,928)	1,479
Balance, shares at Sep. 30, 2017		86,673
AOCI Including Portion Attributable To Non controlling Interest Tax	110
Balance at Dec. 30, 2017	241,921	$ 308,899	28,006	(89,291)	(7,268)	1,575
Balance, shares at Dec. 30, 2017		86,757
Employee Stock Purchase Plan, Value	483	$ 483	0	0	0	0
Employee Stock Purchase Plan, Shares		75
Exercise of options	690	$ 3,588	(2,898)	0	0	0
Exercise of options, shares		368
Dividends Preferred Stock Cash	(5,100)	$ 0	0	(5,100)	0	0
Preferred Stock Accretion To Redemption Value1	(822)	0	0	(822)	0	0
Adjustments Related To Tax Withholding For Share Based Compensation	(574)	0	(574)	0	0	0
Stock based compensation	6,395	0	6,395	0	0	0
Earnings (loss)	(12,124)	0	0	(12,143)	0	19
Currency translation adjustment	(1,836)	0	0	0	(1,976)	140
Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax	305	0	0	0	305	0
Minority Interest Decrease From Redemptions	0
Balance at Sep. 29, 2018	229,592	$ 312,970	30,929	(107,102)	(8,939)	1,734
Balance, shares at Sep. 29, 2018		87,200
Cumulative Effect Of New Accounting Principle In Period Of Adoption	254	$ 0	$ 0	$ 254	$ 0	$ 0
AOCI Including Portion Attributable To Non controlling Interest Tax	$ 130