ORGANIZATION AND BASIS OF PRESENTATION - Other Income And Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Entity Information [Line Items]
Non-service cost component of net benefit cost	$ (13.7)	$ (13.7)	$ (43.7)	$ (40.9)
Other	(6.4)	(6.0)	(14.0)	(16.3)
Other expense	(20.1)	(19.7)	(57.7)	(57.2)
Evergy Kansas Central
Entity Information [Line Items]
Non-service cost component of net benefit cost	(4.1)	(4.9)	(14.1)	(14.5)
Other	(5.6)	(5.9)	(12.8)	(15.4)
Other expense	(9.7)	(10.8)	(26.9)	(29.9)
Evergy Metro
Entity Information [Line Items]
Non-service cost component of net benefit cost	(6.5)	(5.0)	(19.7)	(15.3)
Other	(0.4)	0.1	(0.5)	(0.4)
Other expense	$ (6.9)	$ (4.9)	$ (20.2)	$ (15.7)