FAIR VALUE MEASUREMENTS - Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	$ (43.7)	$ 37.4	$ (87.4)	$ 64.1
Nuclear decommissioning trust - equity securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	(36.8)	34.7	(71.6)	67.8
Nuclear decommissioning trust - debt securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	(3.6)	1.7	(10.1)	(3.4)
Rabbi trusts - equity securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	(3.3)	1.0	(5.7)	(0.3)
Evergy Kansas Central
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	(16.0)	18.1	(34.3)	31.6
Evergy Kansas Central | Nuclear decommissioning trust - equity securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	(13.4)	17.3	(30.1)	31.6
Evergy Kansas Central | Rabbi trusts - equity securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	(2.6)	0.8	(4.2)	0.0
Evergy Metro
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	(27.0)	19.1	(51.6)	32.8
Evergy Metro | Nuclear decommissioning trust - equity securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	(23.4)	17.4	(41.5)	36.2
Evergy Metro | Nuclear decommissioning trust - debt securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	$ (3.6)	$ 1.7	$ (10.1)	$ (3.4)