Basic and Diluted Net Loss Per Common Share - Computation of EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019
Earnings Per Share [Abstract]
Net loss	$ (35,896)	$ (84,767)	$ (196,799)	$ (320,024)
Weighted average common shares outstanding - basic and diluted (in shares)	189,589	179,988	185,737	178,357
Net loss per common share - basic and diluted (in dollars per share)	$ (0.19)	$ (0.47)	$ (1.06)	$ (1.79)