FAIR VALUE MEASUREMENTS - Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized Gain (Loss) on Investments	$ 97.8	$ 67.3	$ 72.3	$ 50.2
Nuclear decommissioning trust - equity securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized Gain (Loss) on Investments	97.0	64.8	72.9	45.5
Nuclear decommissioning trust - debt securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized Gain (Loss) on Investments	(0.1)	1.1	(1.4)	2.6
Rabbi trusts - equity securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized Gain (Loss) on Investments	0.9	1.4	0.8	2.1
Evergy Kansas Central
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized Gain (Loss) on Investments	34.2	26.6	26.7	28.1
Evergy Kansas Central \| Nuclear decommissioning trust - equity securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized Gain (Loss) on Investments	33.3	25.3	25.8	26.2
Evergy Kansas Central \| Rabbi trusts - equity securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized Gain (Loss) on Investments	0.9	1.3	0.9	1.9
Evergy Metro
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized Gain (Loss) on Investments	63.6	40.6	45.7	21.9
Evergy Metro \| Nuclear decommissioning trust - equity securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized Gain (Loss) on Investments	63.7	39.5	47.1	19.3
Evergy Metro \| Nuclear decommissioning trust - debt securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized Gain (Loss) on Investments	$ (0.1)	$ 1.1	$ (1.4)	$ 2.6