Retirement Benefits Plans - Estimated Future Pretax Amounts Recognized From AOCI to Net Periodic Benefit Cost (Details) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
United States pension liabilities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Actuarial loss	$ 142
Prior service cost (credit)	1
Total	143
Non-United States pension liabilities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Actuarial loss	54
Prior service cost (credit)	1
Total	55
Other postretirement liabilities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Actuarial loss	2
Prior service cost (credit)	(14)
Total	$ (12)

The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation.

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=58740216&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Prior Service Cost
-URI http://asc.fasb.org/extlink&oid=49177896

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Amount included in accumulated other comprehensive income (AOCI) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position, including gain (loss), prior service cost (credit), and transition asset (obligation).

+ References

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Amount included in accumulated other comprehensive income (AOCI) related to gain (loss) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position.

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