FAIR VALUE MEASUREMENTS - Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	$ (82.3)	$ 0.3	$ (169.7)	$ 64.4
Nuclear decommissioning trust - equity securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	(74.3)	1.0	(145.9)	68.8
Nuclear decommissioning trust - debt securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	(5.9)	(0.6)	(16.0)	(4.0)
Rabbi trusts - equity securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	(2.1)	(0.1)	(7.8)	(0.4)
Evergy Kansas Central
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	(38.5)	5.2	(72.8)	36.8
Evergy Kansas Central | Nuclear decommissioning trust - equity securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	(37.1)	5.3	(67.2)	36.9
Evergy Kansas Central | Rabbi trusts - equity securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	(1.4)	(0.1)	(5.6)	(0.1)
Evergy Metro
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	(43.1)	(4.9)	(94.7)	27.9
Evergy Metro | Nuclear decommissioning trust - equity securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	(37.2)	(4.3)	(78.7)	31.9
Evergy Metro | Nuclear decommissioning trust - debt securities
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gains (losses)	$ (5.9)	$ (0.6)	$ (16.0)	$ (4.0)