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FAIR VALUE MEASUREMENTS - Gains (Losses) (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] |  |  |
Unrealized gains (losses) | $ 85.5 | $ (145.6) | $ 95.5
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Investment earnings (loss) |  |
Nuclear decommissioning trust - equity securities |  |  |
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] |  |  |
Unrealized gains (losses) | $ 80.4 | (123.3) | 101.8
Nuclear decommissioning trust - debt securities |  |  |
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] |  |  |
Unrealized gains (losses) | 2.7 | (15.2) | (4.5)
Rabbi trusts - equity securities |  |  |
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] |  |  |
Unrealized gains (losses) | 2.4 | (7.1) | (1.8)
Evergy Kansas Central |  |  |
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] |  |  |
Unrealized gains (losses) | $ 30.3 | (68.2) | 49.1
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Investment earnings (loss) |  |
Evergy Kansas Central | Nuclear decommissioning trust - equity securities |  |  |
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] |  |  |
Unrealized gains (losses) | $ 28.3 | (62.8) | 50.5
Evergy Kansas Central | Rabbi trusts - equity securities |  |  |
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] |  |  |
Unrealized gains (losses) | 2.0 | (5.4) | (1.4)
Evergy Metro |  |  |
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] |  |  |
Unrealized gains (losses) | $ 54.8 | (75.7) | 46.8
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Investment earnings (loss) |  |
Evergy Metro | Nuclear decommissioning trust - equity securities |  |  |
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] |  |  |
Unrealized gains (losses) | $ 52.1 | (60.5) | 51.3
Evergy Metro | Nuclear decommissioning trust - debt securities |  |  |
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items] |  |  |
Unrealized gains (losses) | $ 2.7 | $ (15.2) | $ (4.5)

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