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PENSION PLANS AND POST-RETIREMENT BENEFITS PENSION PLANS AND POST-RETIREMENT BENEFITS - Schedule of Components of Net Periodic Benefit Costs (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Total recognized in OCI or regulatory asset/liability $ (4.9) $ (9.5) $ (5.4)
Pension Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 44.9 79.7 82.6
Interest cost 91.9 79.3 84.2
Expected return on plan assets (87.6) (104.0) (103.5)
Prior service cost 1.9 1.9 2.0
Recognized net actuarial (gain) loss (21.5) 34.8 54.1
Settlement and special termination (gain) loss (21.1) 52.8 34.3
Net periodic benefit costs before regulatory adjustment and intercompany allocations 8.5 144.5 153.7
Regulatory adjustment 94.0 14.7 17.3
Net periodic benefit costs (income) 102.5 159.2 171.0
Total recognized in net periodic benefit costs and OCI or regulatory asset/liability 150.3 (298.2) (78.7)
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Total recognized in OCI or regulatory asset/liability 47.8 (457.4) (249.7)
Post-Retirement Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 1.8 3.0 3.3
Interest cost 11.1 7.9 7.8
Expected return on plan assets (11.9) (10.2) (8.9)
Prior service cost 0.1 0.5 0.5
Recognized net actuarial (gain) loss (4.2) (0.3) 1.4
Settlement and special termination (gain) loss 0.0 6.7 0.0
Net periodic benefit costs before regulatory adjustment and intercompany allocations (3.1) 7.6 4.1
Regulatory adjustment (0.1) (7.1) (4.8)
Net periodic benefit costs (income) (3.2) 0.5 (0.7)
Total recognized in net periodic benefit costs and OCI or regulatory asset/liability (12.7) (12.6) (16.1)
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Total recognized in OCI or regulatory asset/liability (9.5) (13.1) (15.4)
Evergy Kansas Central | Pension Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 18.6 30.7 29.1
Interest cost 47.0 38.8 41.0
Expected return on plan assets (44.1) (51.2) (52.8)
Prior service cost 2.0 2.0 2.1
Recognized net actuarial (gain) loss (2.5) 25.6 36.0
Settlement and special termination (gain) loss 1.1 15.6 25.6
Net periodic benefit costs before regulatory adjustment and intercompany allocations 22.1 61.5 81.0
Regulatory adjustment 30.4 0.7 (13.1)
Intercompany allocations (2.3) 2.9 3.2
Net periodic benefit costs (income) 50.2 65.1 71.1
Total recognized in net periodic benefit costs and OCI or regulatory asset/liability 60.6 (148.2) (73.3)
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Total recognized in OCI or regulatory asset/liability 10.4 (213.3) (144.4)
Evergy Kansas Central | Post-Retirement Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 0.9 1.5 1.7
Interest cost 5.7 4.1 4.0
Expected return on plan assets (6.3) (6.5) (6.3)
Prior service cost 0.0 0.4 0.5
Recognized net actuarial (gain) loss (2.0) (0.2) 0.6
Settlement and special termination (gain) loss 0.0 1.4 0.0
Net periodic benefit costs before regulatory adjustment and intercompany allocations (1.7) 0.7 0.5
Regulatory adjustment (1.7) (3.6) (3.3)
Intercompany allocations 0.3 0.3 0.0
Net periodic benefit costs (income) (3.1) (2.6) (2.8)
Total recognized in net periodic benefit costs and OCI or regulatory asset/liability (8.9) (5.8) (13.4)
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Total recognized in OCI or regulatory asset/liability (5.8) (3.2) (10.6)
Evergy Metro      
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Total recognized in OCI or regulatory asset/liability 0.3 0.3 0.3
Evergy Metro | Pension Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 26.3 49.0 53.5
Interest cost 44.0 39.8 42.5
Expected return on plan assets (43.4) (56.4) (55.7)
Prior service cost 0.0 0.0 0.0
Recognized net actuarial (gain) loss (18.2) 38.6 43.8
Settlement and special termination (gain) loss (22.2) 37.2 13.7
Net periodic benefit costs before regulatory adjustment and intercompany allocations (13.5) 108.2 97.8
Regulatory adjustment 63.0 (12.1) 4.2
Intercompany allocations (1.1) (18.4) (25.9)
Net periodic benefit costs (income) 48.4 77.7 76.1
Total recognized in net periodic benefit costs and OCI or regulatory asset/liability 84.6 (187.2) (56.2)
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Total recognized in OCI or regulatory asset/liability 36.2 (264.9) (132.3)
Evergy Metro | Post-Retirement Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 0.9 1.5 1.6
Interest cost 5.5 3.8 3.8
Expected return on plan assets (5.7) (3.7) (2.6)
Prior service cost (0.4) (1.4) (1.0)
Recognized net actuarial (gain) loss (2.1) (0.7) (0.1)
Settlement and special termination (gain) loss 0.0 5.3 0.0
Net periodic benefit costs before regulatory adjustment and intercompany allocations (1.8) 4.8 1.7
Regulatory adjustment 2.1 (1.3) 0.4
Intercompany allocations 0.0 (0.6) (0.4)
Net periodic benefit costs (income) 0.3 2.9 1.7
Total recognized in net periodic benefit costs and OCI or regulatory asset/liability (3.0) (5.0) (1.1)
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Total recognized in OCI or regulatory asset/liability (3.3) (7.9) (2.8)
Actuarial (gain) loss | Pension Benefits      
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax 7.1 (421.4) (195.3)
Amounts reclassified from accumulated other comprehensive loss 21.5 (34.7) (52.4)
Actuarial (gain) loss | Post-Retirement Benefits      
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax (13.6) (13.0) (13.6)
Amounts reclassified from accumulated other comprehensive loss 4.2 0.4 (1.3)
Actuarial (gain) loss | Evergy Kansas Central | Pension Benefits      
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax 11.0 (186.1) (106.3)
Amounts reclassified from accumulated other comprehensive loss 2.5 (25.6) (36.0)
Actuarial (gain) loss | Evergy Kansas Central | Post-Retirement Benefits      
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax (7.8) (3.0) (9.6)
Amounts reclassified from accumulated other comprehensive loss 2.0 0.2 (0.5)
Actuarial (gain) loss | Evergy Metro | Pension Benefits      
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax (4.2) (226.7) (88.4)
Amounts reclassified from accumulated other comprehensive loss 18.2 (38.6) (43.9)
Actuarial (gain) loss | Evergy Metro | Post-Retirement Benefits      
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax (5.8) (10.0) (3.9)
Amounts reclassified from accumulated other comprehensive loss 2.1 0.7 0.1
Prior service cost | Pension Benefits      
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax   (0.6)  
Amounts reclassified from accumulated other comprehensive loss (1.9) (1.9) (2.0)
Net gain (loss) due to settlement 21.1    
Prior service cost | Post-Retirement Benefits      
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax   0.0  
Amounts reclassified from accumulated other comprehensive loss (0.1) (0.5) (0.5)
Net gain (loss) due to settlement 0.0    
Prior service cost | Evergy Kansas Central | Pension Benefits      
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax   (0.4)  
Amounts reclassified from accumulated other comprehensive loss (2.0) (2.0) (2.1)
Net gain (loss) due to settlement (1.1)    
Prior service cost | Evergy Kansas Central | Post-Retirement Benefits      
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax   0.0  
Amounts reclassified from accumulated other comprehensive loss 0.0 (0.4) (0.5)
Net gain (loss) due to settlement 0.0    
Prior service cost | Evergy Metro | Pension Benefits      
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax   (0.4)  
Amounts reclassified from accumulated other comprehensive loss 0.0 0.0 0.0
Net gain (loss) due to settlement 22.2    
Prior service cost | Evergy Metro | Post-Retirement Benefits      
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]      
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax   0.0  
Amounts reclassified from accumulated other comprehensive loss 0.4 $ 1.4 $ 1.0
Net gain (loss) due to settlement $ 0.0