CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 28, 2020	Mar. 30, 2019
Statement of Comprehensive Income [Abstract]
Net loss	$ (99,268)	$ (121,601)
Other comprehensive income (loss), net of tax:
Change in unrealized gain on available-for-sale investments	0	65
Foreign currency translation adjustment	(11,106)	(5,557)
Actuarial gain (loss) on pension liabilities	(394)	78
Net change in accumulated other comprehensive loss	(11,500)	(5,414)
Comprehensive loss	$ (110,768)	$ (127,015)