Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jul. 01, 2018	Apr. 01, 2018	Jun. 30, 2019	Jul. 01, 2018
Net income (loss)	$ (8,734)	$ 21,246	$ (8,965)	$ 12,223	$ 12,512	$ 3,256
Components of other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	130		(145)		285	(300)
Total components of other comprehensive income (loss), net of tax	(130)	(155)	145	154
Comprehensive income (loss)	(8,864)		(8,820)		$ 12,227	$ 3,556
Retained Earnings [Member]
Net income (loss)	$ (8,734)	$ 21,246	$ (8,965)	$ 12,223