Other Comprehensive Income - Schedule of Components of Comprehensive Income (Loss) (Details) $ in Thousands, £ in Millions			3 Months Ended						9 Months Ended
	Apr. 06, 2020 USD ($)	Apr. 06, 2020 GBP (£)	Sep. 26, 2020 USD ($)	Jun. 27, 2020 USD ($)	Mar. 28, 2020 USD ($)	Sep. 28, 2019 USD ($)	Jun. 29, 2019 USD ($)	Mar. 30, 2019 USD ($)	Sep. 26, 2020 USD ($)	Sep. 28, 2019 USD ($)
Other Comprehensive Income (Loss)
Pre-tax			$ 16,691			$ (17,008)			$ (2,970)	$ (14,655)
Tax			(290)			18			(2,555)	29
Total change in other comprehensive income (loss)			16,981	$ (2,417)	$ (14,979)	(17,026)	$ (5,731)	$ 8,073	(415)	(14,684)
Benefit obligation, unamortized actuarial loss	$ 13,400
Pension and postretirement liability and reclassification adjustments
Other Comprehensive Income (Loss)
Pre-tax			273			155			(12,270)	278
Tax			(290)			18			(2,555)	29
Total change in other comprehensive income (loss)			563			137			(9,715)	249
Benefit obligation, unamortized actuarial loss | £		£ 10.9
Foreign currency translation adjustment
Other Comprehensive Income (Loss)
Pre-tax			16,418			(17,163)			9,300	(14,933)
Tax			0			0			0	0
Total change in other comprehensive income (loss)			$ 16,418			$ (17,163)			$ 9,300	$ (14,933)