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FAIR VALUE MEASUREMENTS - Gains (Losses) (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Unrealized gains (losses) $ 33.2 $ (43.7)
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) $ 29.5 (34.8)
Nuclear decommissioning trust - debt securities    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Unrealized gains (losses) 2.1 (6.5)
Rabbi trusts - equity securities    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Unrealized gains (losses) 1.6 (2.4)
Evergy Kansas Central    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Unrealized gains (losses) $ 15.4 (18.3)
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) $ 14.1 (16.7)
Evergy Kansas Central | Rabbi trusts - equity securities    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Unrealized gains (losses) 1.3 (1.6)
Evergy Metro    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Unrealized gains (losses) $ 17.5 (24.6)
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) $ 15.4 (18.1)
Evergy Metro | Nuclear decommissioning trust - debt securities    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Unrealized gains (losses) $ 2.1 $ (6.5)