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PENSION PLANS AND POST-RETIREMENT BENEFITS (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Pension Benefits      
Components of net periodic benefit costs      
Defined benefit plan, benefit obligation, beginning of the year $ 1,850.5 $ 2,561.7  
Service cost 44.9 79.7 $ 82.6
Interest cost 91.9 79.3 84.2
Contribution by participants 0.0 0.0  
Plan amendments   0.6  
Actuarial gain (loss) 64.8 (717.9)  
Benefits paid (84.1) (189.4)  
Special termination benefits   52.8  
Settlements (256.2)    
Other (7.4) (16.3)  
Defined benefit plan, benefit obligation, end of the year 1,704.4 1,850.5 2,561.7
Change in plan assets      
Fair value of plan assets, beginning of the year 1,409.2 1,714.7  
Actual return on plan assets 145.2 (192.6)  
Contributions by employer and participants 36.8 88.4  
Benefits paid (80.2) (185.0)  
Settlements (252.9)    
Other (7.4) (16.3)  
Fair value of plan assets, end of the year 1,250.7 1,409.2 1,714.7
Funded status at end of year (453.7) (441.3)  
Amounts recognized in the consolidated balance sheets      
Non-current asset 0.0 0.0  
Current pension and other post-retirement liability (4.5) (7.2)  
Noncurrent pension liability and other post-retirement liability (449.2) (434.1)  
Net amount recognized before regulatory treatment (453.7) (441.3)  
Accumulated OCI or regulatory asset/liability (92.4) (140.2)  
Net amount recognized as of December 31, 2023 (546.1) (581.5)  
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Accumulated OCI or regulatory asset/liability (92.4) (140.2)  
Pension Benefits | Evergy Kansas Central      
Components of net periodic benefit costs      
Defined benefit plan, benefit obligation, beginning of the year 911.7 1,264.4  
Service cost 18.6 30.7 29.1
Interest cost 47.0 38.8 41.0
Contribution by participants 0.0 0.0  
Plan amendments   0.3  
Actuarial gain (loss) 42.2 (334.3)  
Benefits paid (50.6) (100.1)  
Special termination benefits   15.6  
Settlements (89.3)    
Other (3.4) (3.7)  
Defined benefit plan, benefit obligation, end of the year 876.2 911.7 1,264.4
Change in plan assets      
Fair value of plan assets, beginning of the year 668.5 835.7  
Actual return on plan assets 75.5 (97.1)  
Contributions by employer and participants 15.1 31.2  
Benefits paid (48.2) (97.6)  
Settlements (86.9)    
Other (3.4) (3.7)  
Fair value of plan assets, end of the year 620.6 668.5 835.7
Funded status at end of year (255.6) (243.2)  
Amounts recognized in the consolidated balance sheets      
Non-current asset 0.0 0.0  
Current pension and other post-retirement liability (2.5) (4.7)  
Noncurrent pension liability and other post-retirement liability (253.1) (238.5)  
Net amount recognized before regulatory treatment (255.6) (243.2)  
Accumulated OCI or regulatory asset/liability 60.7 50.3  
Net amount recognized as of December 31, 2023 (194.9) (192.9)  
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Accumulated OCI or regulatory asset/liability 60.7 50.3  
Pension Benefits | Evergy Metro      
Components of net periodic benefit costs      
Defined benefit plan, benefit obligation, beginning of the year 920.6 1,273.5  
Service cost 26.3 49.0 53.5
Interest cost 44.0 39.8 42.5
Contribution by participants 0.0 0.0  
Plan amendments   0.3  
Actuarial gain (loss) 22.0 (378.6)  
Benefits paid (32.3) (88.0)  
Special termination benefits   37.2  
Settlements (166.9)    
Other (4.0) (12.6)  
Defined benefit plan, benefit obligation, end of the year 809.7 920.6 1,273.5
Change in plan assets      
Fair value of plan assets, beginning of the year 740.7 879.0  
Actual return on plan assets 69.7 (95.5)  
Contributions by employer and participants 21.7 57.2  
Benefits paid (32.0) (87.4)  
Settlements (166.0)    
Other (4.0) (12.6)  
Fair value of plan assets, end of the year 630.1 740.7 879.0
Funded status at end of year (179.6) (179.9)  
Amounts recognized in the consolidated balance sheets      
Non-current asset 0.0 0.0  
Current pension and other post-retirement liability (0.5) (1.3)  
Noncurrent pension liability and other post-retirement liability (179.1) (178.6)  
Net amount recognized before regulatory treatment (179.6) (179.9)  
Accumulated OCI or regulatory asset/liability (144.1) (180.3)  
Net amount recognized as of December 31, 2023 (323.7) (360.2)  
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Accumulated OCI or regulatory asset/liability (144.1) (180.3)  
Post-Retirement Benefits      
Components of net periodic benefit costs      
Defined benefit plan, benefit obligation, beginning of the year 201.7 258.4  
Service cost 1.8 3.0 3.3
Interest cost 11.1 7.9 7.8
Contribution by participants 6.2 6.9  
Plan amendments   0.0  
Actuarial gain (loss) (4.0) (58.1)  
Benefits paid (24.0) (23.1)  
Special termination benefits   6.7  
Settlements 0.0    
Other 0.0 0.0  
Defined benefit plan, benefit obligation, end of the year 192.8 201.7 258.4
Change in plan assets      
Fair value of plan assets, beginning of the year 192.9 242.3  
Actual return on plan assets 21.6 (34.9)  
Contributions by employer and participants 9.6 7.0  
Benefits paid (22.6) (21.5)  
Settlements 0.0    
Other 0.0 0.0  
Fair value of plan assets, end of the year 201.5 192.9 242.3
Funded status at end of year 8.7 (8.8)  
Amounts recognized in the consolidated balance sheets      
Non-current asset 24.7 16.8  
Current pension and other post-retirement liability (1.1) (1.3)  
Noncurrent pension liability and other post-retirement liability (14.9) (24.3)  
Net amount recognized before regulatory treatment 8.7 (8.8)  
Accumulated OCI or regulatory asset/liability (34.0) (24.5)  
Net amount recognized as of December 31, 2023 (25.3) (33.3)  
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Accumulated OCI or regulatory asset/liability (34.0) (24.5)  
Post-Retirement Benefits | Evergy Kansas Central      
Components of net periodic benefit costs      
Defined benefit plan, benefit obligation, beginning of the year 103.0 133.9  
Service cost 0.9 1.5 1.7
Interest cost 5.7 4.1 4.0
Contribution by participants 1.0 1.0  
Plan amendments   0.0  
Actuarial gain (loss) (2.6) (28.7)  
Benefits paid (10.2) (10.2)  
Special termination benefits   1.4  
Settlements 0.0    
Other 0.0 0.0  
Defined benefit plan, benefit obligation, end of the year 97.8 103.0 133.9
Change in plan assets      
Fair value of plan assets, beginning of the year 96.2 124.0  
Actual return on plan assets 11.5 (19.2)  
Contributions by employer and participants 1.2 1.1  
Benefits paid (9.8) (9.7)  
Settlements 0.0    
Other 0.0 0.0  
Fair value of plan assets, end of the year 99.1 96.2 124.0
Funded status at end of year 1.3 (6.8)  
Amounts recognized in the consolidated balance sheets      
Non-current asset 5.0 0.0  
Current pension and other post-retirement liability (0.5) (0.6)  
Noncurrent pension liability and other post-retirement liability (3.2) (6.2)  
Net amount recognized before regulatory treatment 1.3 (6.8)  
Accumulated OCI or regulatory asset/liability (18.6) (12.8)  
Net amount recognized as of December 31, 2023 (17.3) (19.6)  
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Accumulated OCI or regulatory asset/liability (18.6) (12.8)  
Post-Retirement Benefits | Evergy Metro      
Components of net periodic benefit costs      
Defined benefit plan, benefit obligation, beginning of the year 98.6 124.5  
Service cost 0.9 1.5 1.6
Interest cost 5.5 3.8 3.8
Contribution by participants 5.2 5.8  
Plan amendments   0.0  
Actuarial gain (loss) (1.4) (29.4)  
Benefits paid (13.8) (12.9)  
Special termination benefits   5.3  
Settlements 0.0    
Other 0.0 0.0  
Defined benefit plan, benefit obligation, end of the year 95.0 98.6 124.5
Change in plan assets      
Fair value of plan assets, beginning of the year 96.7 118.3  
Actual return on plan assets 10.1 (15.7)  
Contributions by employer and participants 8.4 5.9  
Benefits paid (12.8) (11.8)  
Settlements 0.0    
Other 0.0 0.0  
Fair value of plan assets, end of the year 102.4 96.7 $ 118.3
Funded status at end of year 7.4 (1.9)  
Amounts recognized in the consolidated balance sheets      
Non-current asset 19.7 16.8  
Current pension and other post-retirement liability (0.6) (0.7)  
Noncurrent pension liability and other post-retirement liability (11.7) (18.0)  
Net amount recognized before regulatory treatment 7.4 (1.9)  
Accumulated OCI or regulatory asset/liability (21.7) (18.4)  
Net amount recognized as of December 31, 2023 (14.3) (20.3)  
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Accumulated OCI or regulatory asset/liability (21.7) (18.4)  
Actuarial (gain) loss | Pension Benefits      
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Actuarial (gain) loss (104.1) (153.8)  
Actuarial (gain) loss | Pension Benefits | Evergy Kansas Central      
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Actuarial (gain) loss 47.3 35.0  
Actuarial (gain) loss | Pension Benefits | Evergy Metro      
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Actuarial (gain) loss (142.8) (179.0)  
Actuarial (gain) loss | Post-Retirement Benefits      
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Actuarial (gain) loss (34.7) (25.3)  
Actuarial (gain) loss | Post-Retirement Benefits | Evergy Kansas Central      
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Actuarial (gain) loss (19.0) (13.2)  
Actuarial (gain) loss | Post-Retirement Benefits | Evergy Metro      
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Actuarial (gain) loss (16.9) (13.1)  
Prior service cost | Pension Benefits      
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Prior service cost 11.7 13.6  
Prior service cost | Pension Benefits | Evergy Kansas Central      
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Prior service cost 13.4 15.3  
Prior service cost | Pension Benefits | Evergy Metro      
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Prior service cost (1.3) (1.3)  
Prior service cost | Post-Retirement Benefits      
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Prior service cost 0.7 0.8  
Prior service cost | Post-Retirement Benefits | Evergy Kansas Central      
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Prior service cost 0.4 0.4  
Prior service cost | Post-Retirement Benefits | Evergy Metro      
Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost:      
Prior service cost $ (4.8) $ (5.3)