Employee Benefits - Components of Plan Benefit Expense Narrative (Details) - UNITED STATES - USD ($) $ in Millions		3 Months Ended			9 Months Ended
	Jul. 28, 2019	Sep. 26, 2020	Jun. 27, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019
Pension
Defined Benefit Plan Disclosure [Line Items]
Curtailment (gain) loss	$ (11)		$ (7)
Recognized net (gain) loss		$ 7		$ 15	$ 15	$ 26
Pension | Mark-to-Market Loss
Defined Benefit Plan Disclosure [Line Items]
Recognized net (gain) loss	8		$ 49
Other Nonpension Postretirement
Defined Benefit Plan Disclosure [Line Items]
Curtailment (gain) loss	(6)
Other Nonpension Postretirement | Mark-to-Market Loss
Defined Benefit Plan Disclosure [Line Items]
Recognized net (gain) loss	$ (55)
Maximum [Member] | Pension
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	7.50%
Maximum [Member] | Other Nonpension Postretirement
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	7.50%
Minimum [Member] | Pension
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	7.00%
Minimum [Member] | Other Nonpension Postretirement
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	7.00%