PENSION PLANS AND POST-RETIREMENT BENEFITS PENSION PLANS AND POST-RETIREMENT BENEFITS - Schedule of Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]
Total recognized in OCI or regulatory asset/liability	$ (1.3)	$ (1.3)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	11.5	11.2
Interest cost	22.4	22.4
Expected return on plan assets	(21.7)	(21.8)
Prior service cost	0.5	0.5
Recognized net actuarial (gain) loss	(4.3)	(5.6)
Settlement and special termination (gain) loss	0.0	(15.9)
Net periodic benefit costs before regulatory adjustment and intercompany allocations	8.4	(9.2)
Regulatory adjustment	5.7	33.5
Intercompany allocations	0.0	0.0
Net periodic benefit costs (income)	14.1	24.3
Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.4	0.4
Interest cost	2.5	2.8
Expected return on plan assets	(2.8)	(3.0)
Prior service cost	0.0	0.0
Recognized net actuarial (gain) loss	(1.0)	(1.0)
Settlement and special termination (gain) loss		0.0
Net periodic benefit costs before regulatory adjustment and intercompany allocations	(0.9)	(0.8)
Regulatory adjustment	0.0	(0.1)
Intercompany allocations	0.0	0.0
Net periodic benefit costs (income)	(0.9)	(0.9)
Evergy Kansas Central | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	4.7	4.6
Interest cost	11.4	11.4
Expected return on plan assets	(10.7)	(11.0)
Prior service cost	0.5	0.5
Recognized net actuarial (gain) loss	0.2	(0.8)
Settlement and special termination (gain) loss	0.0	0.4
Net periodic benefit costs before regulatory adjustment and intercompany allocations	6.1	5.1
Regulatory adjustment	(2.1)	7.4
Intercompany allocations	(0.4)	(0.5)
Net periodic benefit costs (income)	3.6	12.0
Evergy Kansas Central | Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.2	0.2
Interest cost	1.3	1.4
Expected return on plan assets	(1.5)	(1.5)
Prior service cost	0.0	0.0
Recognized net actuarial (gain) loss	(0.5)	(0.5)
Settlement and special termination (gain) loss		0.0
Net periodic benefit costs before regulatory adjustment and intercompany allocations	(0.5)	(0.4)
Regulatory adjustment	0.2	(0.6)
Intercompany allocations	0.0	0.1
Net periodic benefit costs (income)	(0.3)	(0.9)
Evergy Metro
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax [Abstract]
Total recognized in OCI or regulatory asset/liability	0.1	0.1
Evergy Metro | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	6.8	6.6
Interest cost	10.7	10.8
Expected return on plan assets	(10.9)	(10.8)
Prior service cost	0.0	0.0
Recognized net actuarial (gain) loss	(4.4)	(4.6)
Settlement and special termination (gain) loss	0.0	(16.3)
Net periodic benefit costs before regulatory adjustment and intercompany allocations	2.2	(14.3)
Regulatory adjustment	7.7	25.9
Intercompany allocations	(0.5)	(0.2)
Net periodic benefit costs (income)	9.4	11.4
Evergy Metro | Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.2	0.2
Interest cost	1.2	1.3
Expected return on plan assets	(1.4)	(1.4)
Prior service cost	(0.1)	(0.1)
Recognized net actuarial (gain) loss	(0.4)	(0.5)
Settlement and special termination (gain) loss		0.0
Net periodic benefit costs before regulatory adjustment and intercompany allocations	(0.5)	(0.5)
Regulatory adjustment	(0.1)	0.6
Intercompany allocations	0.1	0.0
Net periodic benefit costs (income)	$ (0.5)	$ 0.1