RETIREMENT BENEFITS - Health Care Cost-Trend Rate (Details)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans
Health care cost increase following year (as a percent)	6.50%	6.75%
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	2027	2027
Non-U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans
Health care cost increase following year (as a percent)	6.85%	6.85%
Ultimate rate to which cost increase is assumed to decline (as a percent)	6.85%	6.85%
Year in which the ultimate rate is reached	2021	2020

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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (l)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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Ultimate trend rate for health care cost for defined benefit postretirement plan.

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

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