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PENSION PLANS AND POST-RETIREMENT BENEFITS - Cost Trend Assumptions (Details) - Post-Retirement Benefits | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Assumed annual health care cost growth rates |  |
Health care cost trend rate assumed for next year | 6.00% | 6.30%
Rate to which the cost trend is assumed to decline (the ultimate trend rate) | 4.50% | 4.50%
Year that rate reaches ultimate trend | 2027 | 2027
Evergy Metro |  |
Assumed annual health care cost growth rates |  |
Health care cost trend rate assumed for next year | 6.00% | 6.30%
Rate to which the cost trend is assumed to decline (the ultimate trend rate) | 4.50% | 4.50%
Year that rate reaches ultimate trend | 2027 | 2027
Evergy Kansas Central |  |
Assumed annual health care cost growth rates |  |
Health care cost trend rate assumed for next year | 6.00% | 6.30%
Rate to which the cost trend is assumed to decline (the ultimate trend rate) | 4.50% | 4.50%
Year that rate reaches ultimate trend | 2027 | 2027

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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/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 + Details
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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/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 + Details
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- Definition Year ultimate health care cost trend rate is expected to be reached, in CCYY format. + References 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 + Details
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