Retirement Benefits (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 25, 2020	Dec. 27, 2019
Pension Benefits
Components of net periodic benefit cost
Service cost-benefits earned during the period	$ 9,355	$ 9,361	$ 7,735
Interest cost on projected benefit obligation	11,409	13,313	15,103
Expected return on assets	(20,767)	(18,814)	(17,152)
Amortization of prior service cost (credit)	246	294	279
Amortization of net loss (gain)	9,248	10,243	8,392
Settlement loss (gain)	12,285	0	0
Cost of pension plans which are not significant and have not adopted ASC 715	368	168	110
Net periodic benefit cost	22,144	14,565	14,467
Postretirement Medical Benefits
Components of net periodic benefit cost
Service cost-benefits earned during the period	670	609	545
Interest cost on projected benefit obligation	832	1,016	1,162
Expected return on assets	0	0	0
Amortization of prior service cost (credit)	0	0	0
Amortization of net loss (gain)	1,002	733	273
Settlement loss (gain)	0	0	0
Net periodic benefit cost	2,504	2,358	1,980
Accounting Standards Update 2017-07 [Member]
Defined Benefit Plan Disclosure [Line Items]
Non-service pension cost included in non-operating expense	$ 12,000	$ 5,000	$ 5,000