Retirement Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 04, 2021	Jun. 28, 2020	Jul. 04, 2021	Jun. 28, 2020
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 29	$ 30	$ 59	$ 59
Interest cost	90	123	180	246
Expected return on plan assets	(241)	(235)	(482)	(469)
Net actuarial loss (gain)	80	71	183	140
Prior service credit	(5)	(5)	(10)	(9)
Net periodic benefit credit	(47)	(16)	(70)	(33)
Other Post-retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	3	3	5	5
Interest cost	4	7	9	14
Expected return on plan assets	(9)	(9)	(18)	(18)
Net actuarial loss (gain)	0	(1)	0	(2)
Prior service credit	0	0	0	0
Net periodic benefit credit	$ (2)	$ 0	$ (4)	$ (1)