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LONG-TERM DEBT - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2020 | May 31, 2020 | Apr. 30, 2020 | Dec. 31, 2019
Secured Debt | Mortgage Bonds Due 2050 EKC |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 3.45% |  |  |
Long-term debt gross | $ 500.0 |  |  |
Secured Debt | Mortgage Bonds Due 2020 EKC |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate |  |  |  | 5.10%
Long-term debt gross |  |  |  | $ 250.0
Secured Debt | Mortgage Bonds Due 2030 EM |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 2.25% |  |  |
Long-term debt gross | $ 400.0 |  |  |
Evergy Kansas Central |  |  |  |
Debt Instrument [Line Items] |  |  |  |
AdditionalPrincipalFirstMortgageBondsAvailableToBeIssued | 780.6 |  |  |
Evergy Kansas Central | Secured Debt | Mortgage Bonds Due 2050 EKC |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate |  |  | 3.45% |
Long-term debt gross | 500.0 |  | $ 500.0 |
Evergy Kansas Central | Secured Debt | Mortgage Bonds Due 2020 EKC |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate |  |  | 5.10% |
Long-term debt gross |  |  | $ 250.0 | 250.0
Evergy Kansas Central | Secured Debt | Mortgage Bonds Due 2030 EM |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt gross | 0.0 |  |  |
Evergy Metro |  |  |  |
Debt Instrument [Line Items] |  |  |  |
AdditionalPrincipalFirstMortgageBondsAvailableToBeIssued | $ 4,733.1 |  |  |
Percentage of Bondable Property Allowed | 75.00% |  |  |
Evergy Metro | Secured Debt | Mortgage Bonds Due 2050 EKC |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt gross | $ 0.0 |  |  |
Evergy Metro | Secured Debt | Mortgage Bonds Due 2020 EKC |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt gross |  |  |  | $ 0.0
Evergy Metro | Secured Debt | Mortgage Bonds Due 2030 EM |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate |  | 2.25% |  |
Long-term debt gross | 400.0 | $ 400.0 |  |
Evergy Kansas South Inc |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Maximum Amount Of First Mortgage Bonds Authorized | 3,500.0 |  |  |
AdditionalPrincipalFirstMortgageBondsAvailableToBeIssued | $ 2,828.6 |  |  |

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