Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2017	Sep. 30, 2016	Sep. 29, 2017	Sep. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net Income (loss)	$ 40	$ (16,183)	$ 1,225	$ (35,781)
Foreign currency adjustment	671	129	2,150	299
Change in pension loss, net of taxes of $14 and $17 in the 2017 and 2016 third quarters, respectively, and $43 and $48 in the first three quarters of 2017 and 2016, respectively	(205)	(9)	(718)	(25)
Other comprehensive income	466	120	1,432	274
Comprehensive income (loss)	$ 506	$ (16,063)	$ 2,657	$ (35,507)