Employee Benefits - Components of Plan Benefit Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 9	$ 22	$ 27	$ 66
Interest cost	42	41	131	124
Expected return on plan assets	(86)	(91)	(254)	(273)
Amortization of unrecognized prior service cost (gain)	1	2	5	6
Recognized net (gain) loss	23	(36)	34	(47)
Net periodic benefit cost	(11)	(62)	(57)	(124)
Curtailment (gain) loss	(11)	(30)	(11)	(30)
Total plan benefit (income) expense	(22)	(92)	(68)	(154)
Other Nonpension Postretirement
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	5	12	14
Interest cost	10	10	30	28
Expected return on plan assets	(23)	(22)	(65)	(69)
Amortization of unrecognized prior service cost (gain)	(2)	(3)	(6)	(7)
Recognized net (gain) loss	(55)	0	(55)	0
Net periodic benefit cost	(65)	(10)	(84)	(34)
Curtailment (gain) loss	(6)	0	(6)	0
Total plan benefit (income) expense	(71)	(10)	(90)	(34)
Postemployment
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	3	3
Interest cost	0	0	1	0
Recognized net (gain) loss	(1)	(1)	(3)	(3)
Total plan benefit (income) expense	$ 0	$ 0	$ 1	$ 0