CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 26, 2021	Jun. 27, 2020	Jun. 26, 2021	Jun. 27, 2020
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 82,095	$ (8,991)	$ 139,808	$ 15,653
Other comprehensive income (loss):
Pension and postemployment adjustment, net of tax	329	(10,839)	783	(10,278)
Foreign currency translation adjustments	5,125	8,422	(200)	(7,118)
Comprehensive income (loss)	$ 87,549	$ (11,408)	$ 140,391	$ (1,743)