Pension, Retiree Medical and Savings Plans Pension, Retiree Medical and Savings Plans (Target Asset Allocations) (Details)	Dec. 25, 2021	Dec. 26, 2020
Fixed Income
Target Asset Allocation [Line Items]
Target investment allocation percentage		50.00%
U.S. Equity
Target Asset Allocation [Line Items]
Target investment allocation percentage		25.00%
International Equity
Target Asset Allocation [Line Items]
Target investment allocation percentage		21.00%
Real Estate Funds [Member]
Target Asset Allocation [Line Items]
Target investment allocation percentage		4.00%
Forecast [Member] | Fixed Income
Target Asset Allocation [Line Items]
Target investment allocation percentage	51.00%
Forecast [Member] | U.S. Equity
Target Asset Allocation [Line Items]
Target investment allocation percentage	24.00%
Forecast [Member] | International Equity
Target Asset Allocation [Line Items]
Target investment allocation percentage	21.00%
Forecast [Member] | Real Estate Funds [Member]
Target Asset Allocation [Line Items]
Target investment allocation percentage	4.00%