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PENSION PLANS AND POST-RETIREMENT BENEFITS - APBO (Details) - USD ($)
$ in Millions
Dec. 31, 2023
Dec. 31, 2022
Pension Benefits    
Defined Benefit Plan Disclosure [Line Items]    
ABO for all defined benefit pension plans $ 1,539.7 $ 1,687.3
Pension plans with the PBO in excess of plan assets    
Projected benefit obligation 1,704.4 1,850.5
Fair value of plan assets 1,250.7 1,409.2
Other post-retirement benefit plans with the APBO in excess of plan assets    
Accumulated benefit obligation 1,539.7 1,687.3
Fair value of plan assets 1,250.7 1,409.2
Post-Retirement Benefits    
Other post-retirement benefit plans with the APBO in excess of plan assets    
Accumulated benefit obligation 82.6 201.7
Fair value of plan assets 66.9 192.9
Evergy Kansas Central | Pension Benefits    
Defined Benefit Plan Disclosure [Line Items]    
ABO for all defined benefit pension plans 809.9 844.4
Pension plans with the PBO in excess of plan assets    
Projected benefit obligation 876.2 911.7
Fair value of plan assets 620.6 668.5
Other post-retirement benefit plans with the APBO in excess of plan assets    
Accumulated benefit obligation 809.9 844.4
Fair value of plan assets 620.6 668.5
Evergy Kansas Central | Post-Retirement Benefits    
Other post-retirement benefit plans with the APBO in excess of plan assets    
Accumulated benefit obligation 3.5 103.0
Fair value of plan assets 0.0 96.2
Evergy Metro | Pension Benefits    
Defined Benefit Plan Disclosure [Line Items]    
ABO for all defined benefit pension plans 711.3 824.6
Pension plans with the PBO in excess of plan assets    
Projected benefit obligation 809.7 920.6
Fair value of plan assets 630.1 740.7
Other post-retirement benefit plans with the APBO in excess of plan assets    
Accumulated benefit obligation 711.3 824.6
Fair value of plan assets 630.1 740.7
Evergy Metro | Post-Retirement Benefits    
Other post-retirement benefit plans with the APBO in excess of plan assets    
Accumulated benefit obligation 79.1 98.6
Fair value of plan assets $ 66.9 $ 96.7