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PENSION PLANS AND POST-RETIREMENT BENEFITS - Weighted-Average Assumptions (Details) | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Pension Benefits |  |
Weighted-average assumptions used to determine the benefit obligation |  |
Discount rate | 2.95% | 3.62%
Rate of compensation increase | 3.71% | 3.74%
Interest crediting rate for cash balance plans | 4.12% | 4.32%
Weighted-average assumptions used to determine net costs |  |
Discount rate | 3.62% | 4.35%
Expected long-term return on plan assets | 6.63% | 6.61%
Rate of compensation increase | 3.74% | 3.76%
Interest crediting rate for cash balance plans | 4.32% | 4.32%
Post-Retirement Benefits |  |
Weighted-average assumptions used to determine the benefit obligation |  |
Discount rate | 2.84% | 3.56%
Rate of compensation increase | 3.75% | 3.75%
Weighted-average assumptions used to determine net costs |  |
Discount rate | 3.56% | 4.33%
Expected long-term return on plan assets | 4.19% | 4.44%
Rate of compensation increase | 3.75% | 3.50%
Evergy Kansas Central | Pension Benefits |  |
Weighted-average assumptions used to determine the benefit obligation |  |
Discount rate | 2.93% | 3.61%
Rate of compensation increase | 3.76% | 3.78%
Interest crediting rate for cash balance plans | 4.00% | 4.21%
Weighted-average assumptions used to determine net costs |  |
Discount rate | 3.61% | 4.35%
Expected long-term return on plan assets | 6.70% | 6.75%
Rate of compensation increase | 3.75% | 4.03%
Interest crediting rate for cash balance plans | 4.21% | 4.21%
Evergy Kansas Central | Post-Retirement Benefits |  |
Weighted-average assumptions used to determine the benefit obligation |  |
Discount rate | 2.80% | 3.54%
Weighted-average assumptions used to determine net costs |  |
Discount rate | 3.54% | 4.33%
Expected long-term return on plan assets | 6.00% | 6.00%
Evergy Metro | Pension Benefits |  |
Weighted-average assumptions used to determine the benefit obligation |  |
Discount rate | 2.97% | 3.64%
Rate of compensation increase | 3.71% | 3.71%
Interest crediting rate for cash balance plans | 4.46% | 4.50%
Weighted-average assumptions used to determine net costs |  |
Discount rate | 3.64% | 4.36%
Expected long-term return on plan assets | 6.56% | 6.47%
Rate of compensation increase | 3.71% | 3.64%
Interest crediting rate for cash balance plans | 4.50% | 4.50%
Evergy Metro | Post-Retirement Benefits |  |
Weighted-average assumptions used to determine the benefit obligation |  |
Discount rate | 2.88% | 3.58%
Rate of compensation increase | 3.75% | 3.75%
Weighted-average assumptions used to determine net costs |  |
Discount rate | 3.58% | 4.33%
Expected long-term return on plan assets | 2.37% | 2.94%
Rate of compensation increase | 3.75% | 3.50%

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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit 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 (k)(1) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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- Definition Weighted average rate increase of compensation, used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit 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 (k)(2) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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- Definition Weighted-average interest crediting rate used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, cash balance and other defined benefit plans with promised interest crediting rate. + 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 (k)(4) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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- Definition Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit 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 (k)(3) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2919-114920 + Details
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