Retirement Plans - Benefits Plans (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jul. 01, 2018	Jul. 02, 2017	Jul. 01, 2018	Jul. 02, 2017
Defined Benefit Plan Disclosure [Line Items]
Required employer contributions to defined-benefit retirement plans during the fiscal year	$ 315		$ 315
Expected future employer contributions to defined-benefit retirement plans during the fiscal year	570		570
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	44	$ 42	90	$ 84
Interest cost	140	113	254	226
Expected return on plan assets	(228)	(170)	(407)	(339)
Recognized net actuarial loss (gain)	93	86	189	172
Amortization of prior service credit	(11)	(16)	(22)	(33)
Net periodic benefit cost (credit)	38	55	104	110
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	3	5	6
Interest cost	8	9	16	17
Expected return on plan assets	(10)	(9)	(19)	(17)
Recognized net actuarial loss (gain)	(1)	(1)	(2)	(2)
Amortization of prior service credit	(1)	(1)	(2)	(2)
Net periodic benefit cost (credit)	$ (2)	$ 1	$ (2)	$ 2

Defined Benefit Plan, Expected Future Discretionary Employer Contributions, Current Fiscal Year

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- Definition

Defined Benefit Plan, Expected Future Required Employer Contributions, Current Fiscal Year

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- Definition

Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan.

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Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) of defined benefit plan.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan.

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Amount of cost recognized for passage of time related to defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)(2)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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Amount of net periodic benefit cost (credit) for defined benefit plan.

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Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)(1)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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