Retirement Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 27, 2020	Sep. 29, 2019	Sep. 27, 2020	Sep. 29, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 29	$ 28	$ 88	$ 84
Interest cost	123	150	369	450
Expected return on plan assets	(234)	(228)	(703)	(684)
Recognized net actuarial loss (gain)	87	98	246	238
Amortization of prior service credit	(4)	(4)	(13)	(13)
Net periodic benefit cost (credit)	1	44	(13)	75
Other Post-retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	2	7	6
Interest cost	7	9	21	27
Expected return on plan assets	(9)	(9)	(27)	(27)
Recognized net actuarial loss (gain)	0	(2)	(2)	(6)
Amortization of prior service credit	(1)	(1)	(1)	(3)
Net periodic benefit cost (credit)	$ (1)	$ (1)	$ (2)	$ (3)