Employee Benefits - Components of Plan Benefit Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 22	$ 25
Interest cost	42	41
Expected return on plan assets	(92)	(90)
Amortization of unrecognized prior service (gain)	2	2
Recognized net (gain) loss	(9)	3
Net periodic benefit cost	(35)	(19)
Curtailment (gain) loss	0	1
Total plan benefit (income) expense	(35)	(18)
Other Nonpension Postretirement
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	5
Interest cost	9	9
Expected return on plan assets	(24)	(24)
Amortization of unrecognized prior service (gain)	(2)	(2)
Recognized net (gain) loss	0	(29)
Net periodic benefit cost	(12)	(41)
Curtailment (gain) loss	0	3
Total plan benefit (income) expense	(12)	(38)
Postemployment
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1
Interest cost	0	1
Recognized net (gain) loss	(1)	1
Total plan benefit (income) expense	$ 0	$ 3