Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jul. 01, 2016	Jun. 30, 2017	Jul. 01, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net Income (loss)	$ 434	$ 1,259	$ 1,185	$ (19,598)
Foreign currency adjustment	1,215	(511)	1,479	170
Change in pension loss, net of taxes of $15 and $16 in the 2017 and 2016 second quarters, respectively, and $29 and $31 in the first two quarters of 2017 and 2016, respectively	(445)	179	(513)	(16)
Other comprehensive income (loss)	770	(332)	966	154
Comprehensive income (loss)	$ 1,204	$ 927	$ 2,151	$ (19,444)