Employee Benefits - Contributions to Employee Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018	Dec. 29, 2018
Defined Benefit Plan Disclosure [Line Items]
Employer contributions to employee benefit plans	$ 7	$ 255	$ 12	$ 274	$ 287
Total current year projected employer contributions	25		25
Employer discretionary contribution amount		250
Pension
Defined Benefit Plan Disclosure [Line Items]
Employer contributions to employee benefit plans	3	251	4	266	270
Total current year projected employer contributions	7		7
Nonpension postretirement
Defined Benefit Plan Disclosure [Line Items]
Employer contributions to employee benefit plans	4	4	8	$ 8	$ 17
Total current year projected employer contributions	$ 18		$ 18
United States | Pension
Defined Benefit Plan Disclosure [Line Items]
Employer discretionary contribution amount		$ 250