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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