Employee Benefits - Contributions to Employee Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018	Dec. 29, 2018
Defined Benefit Plan Disclosure [Line Items]
Employer contributions to employee benefit plans	$ 7	$ 5	$ 19	$ 279	$ 287
Total current year projected employer contributions	25		25
Pension
Defined Benefit Plan Disclosure [Line Items]
Employer contributions to employee benefit plans	2	0	6	266	270
Total current year projected employer contributions	7		7
Nonpension postretirement
Defined Benefit Plan Disclosure [Line Items]
Employer contributions to employee benefit plans	5	5	13	$ 13	$ 17
Total current year projected employer contributions	$ 18		$ 18
UNITED STATES | Pension
Defined Benefit Plan Disclosure [Line Items]
Employer discretionary contribution amount		$ 250