Employee Benefits - Components of Plan Benefit Expense (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 22	$ 25	$ 72	$ 74
Interest cost		40	43	123	131
Expected return on plan assets		(97)	(87)	(277)	(266)
Amortization of unrecognized prior service (gain)		3	3	7	10
Recognized net (gain) loss		83	28	84	28
Net periodic benefit cost		51	12	9	(23)
Curtailment (gain) loss		(134)	0	(136)	0
Total plan benefit (income) expense		(83)	12	(127)	(23)
Other Nonpension Postretirement
Defined Benefit Plan Disclosure [Line Items]
Service cost		5	5	14	15
Interest cost		10	10	28	29
Expected return on plan assets		(24)	(22)	(73)	(67)
Amortization of unrecognized prior service (gain)		(3)	(2)	(7)	(7)
Recognized net (gain) loss		0	0	(29)	0
Net periodic benefit cost		(12)	(9)	(67)	(30)
Curtailment (gain) loss		0	0	3	0
Total plan benefit (income) expense		(12)	(9)	(64)	(30)
Postemployment
Defined Benefit Plan Disclosure [Line Items]
Service cost		1	1	4	5
Interest cost		0	1	2	3
Recognized net (gain) loss		0	1	1	3
Total plan benefit (income) expense		$ 1	$ 3	$ 7	$ 11
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	3.00%
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	7.00%