Postemployment Benefits Postretirement Benefit Plans - Net Cost/(Benefit) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service costs/(credits)			$ (229)	$ (261)
Postretirement Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1	$ 2	4	6
Interest cost	12	11	35	33
Expected return on plan assets	(13)	(12)	(40)	(37)
Amortization of prior service costs/(credits)	(77)	(77)	(230)	(233)
Amortization of unrecognized losses/(gains)	(2)	0	(6)	0
Curtailments	(4)	0	(4)	0
Net cost/(benefit)	$ (83)	$ (76)	$ (241)	$ (231)