Pension and Other Postretirement Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 15	$ 14	$ 43	$ 41
Interest cost	20	19	61	62
Expected return on plan assets	(20)	(19)	(59)	(88)
Amortization of unrecognized prior service credit	(24)	(26)	(74)	(79)
Net loss amortization	0	1	1	1
Termination benefits	0	1	1	1
Curtailments	(1)	(5)	(6)	(7)
Net periodic benefit cost	(10)	(15)	(33)	(69)
International \| Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	66	59	189	179
Interest cost	44	51	127	155
Expected return on plan assets	(101)	(95)	(292)	(288)
Amortization of unrecognized prior service credit	(3)	(3)	(8)	(9)
Net loss amortization	25	21	72	64
Termination benefits	1	1	2	2
Curtailments	(1)	(2)	(1)	(1)
Net periodic benefit cost	31	32	89	102
U.S. \| Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	80	66	234	212
Interest cost	114	116	341	342
Expected return on plan assets	(210)	(203)	(646)	(623)
Amortization of unrecognized prior service credit	(13)	(14)	(40)	(41)
Net loss amortization	46	32	135	89
Termination benefits	3	6	11	11
Curtailments	4	3	8	3
Net periodic benefit cost	$ 24	$ 6	$ 43	$ (7)

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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Amount of cost of providing special or contractual termination benefits payable from 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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- Definition

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

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-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 gain (loss) recognized in net periodic benefit (cost) credit from event reducing expected years of future service of present employees or eliminating accrual of defined benefits for some or all future services of present employees.

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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
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-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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