RETIREMENT BENEFITS - Health Care Cost-Trend Rate (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans
Health care cost increase following year (as a percent)	6.50%	6.50%
Ultimate rate to which cost increase is assumed to decline (as a percent)	5.00%	5.00%
Year in which the ultimate rate is reached	2023	2023
U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans
Health care cost increase following year (as a percent)	6.50%	6.50%
Ultimate rate to which cost increase is assumed to decline (as a percent)	5.00%	5.00%
Year in which the ultimate rate is reached	2023	2023
Effect of one-percentage-point increase of benefits earned and interest cost for U.S. postretirement plans	$ 1	$ 1
Effect of one-percentage-point decrease on benefits earned and interest cost for U.S. postretirement plans	(1)	(1)
Effect of one-percentage-point increase on accumulated postretirement benefit obligation for U.S. postretirement plans	33	30
Effect of one-percentage-point decrease on accumulated postretirement benefit obligation for U.S. postretirement plans	$ (29)	$ (26)
Non-U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans
Health care cost increase following year (as a percent)	6.87%	6.86%
Ultimate rate to which cost increase is assumed to decline (as a percent)	6.87%	6.85%
Effect of one-percentage-point increase of benefits earned and interest cost for U.S. postretirement plans	$ 13	$ 12
Effect of one-percentage-point decrease on benefits earned and interest cost for U.S. postretirement plans	(10)	(10)
Effect of one-percentage-point increase on accumulated postretirement benefit obligation for U.S. postretirement plans	150	144
Effect of one-percentage-point decrease on accumulated postretirement benefit obligation for U.S. postretirement plans	$ (125)	$ (118)
Non-U.S. \| Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans
Year in which the ultimate rate is reached	2018	2017
Non-U.S. \| Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans
Year in which the ultimate rate is reached	2019	2029

Amount of decrease in accumulated postretirement benefit obligation from one-percentage-point decrease in assumed health care cost trend rate.

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

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Amount of decrease in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point decrease in assumed health care cost trend rate.

+ References

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Amount of increase in accumulated postretirement benefit obligation from one-percentage-point increase in assumed health care cost trend rate.

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- Definition

Assumed rate, for next fiscal year, based on annual change in cost of health care cost benefits used to measure expected cost of benefits covered by defined benefit postretirement plan. Factors include, but are not limited to, estimate of health care inflation, change in health care utilization or delivery pattern, technological advances, and change in health status of participant. Excludes factors for change in composition of plan population by age and dependency status.

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

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- Definition

Ultimate trend rate for health care cost for defined benefit postretirement 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 (l)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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Year ultimate health care cost trend rate is expected to be reached, in CCYY format.

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

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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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