RETIREMENT BENEFITS Benefits - Assumed Health Care Cost Trend Rates Used (Details)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Postemployment Benefits [Abstract]
Health care cost trend rate	8.49%	8.10%
Rate to which the cost trend is assumed to decline (the ultimate trend rate)	4.85%	4.95%
Year that the rate reaches the ultimate trend rate	2026	2025

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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (l)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

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- Definition

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

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- Definition

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

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- References

No definition available.

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