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FAIR VALUE MEASUREMENTS - Gains (Losses) (Details) - USD ($)
$ in Millions
12 Months Ended
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)