Common and Preferred Stock Transfers out of accumulated comprehensive income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Stockholders' Equity Attributable to Parent	$ 527,403	$ 457,926	$ 468,544	$ 513,143
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	8,483	808	(22,666)
Foreign currency translation adjustments	7,845	808	(22,666)
Accumulated other comprehensive loss	(26,537)	(34,382)	(35,190)	$ (12,524)
Accumulated Other Comprehensive (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Foreign currency translation adjustments	7,845	808	(22,666)
Other Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ (638)	$ 0	$ 0