UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 27, 2020	Sep. 29, 2019	Sep. 27, 2020	Sep. 29, 2019
Statement of Comprehensive Income [Abstract]
Net loss	$ (17,459)	$ (30,590)	$ (86,041)	$ (105,566)
Other comprehensive income (loss), before tax:
Unrealized gain (loss) on derivative instruments	(9)	22	16	0
Unrealized gain (loss) on available-for-sale securities	(14)	(27)	(23)	46
Total other comprehensive income (loss), before tax	(23)	(5)	(7)	46
Tax benefit (provision) related to derivative instruments	0	0	0	0
Total other comprehensive income (loss), net of tax	(23)	(5)	(7)	46
Comprehensive loss	$ (17,482)	$ (30,595)	$ (86,048)	$ (105,520)