ORGANIZATION AND BASIS OF PRESENTATION - Other Income And Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Entity Information [Line Items]
Non-service cost component of net benefit cost	$ (13.8)	$ (14.1)	$ (30.0)	$ (27.2)
Other	(1.1)	(4.0)	(7.6)	(10.3)
Other expense	(14.9)	(18.1)	(37.6)	(37.5)
Evergy Kansas Central
Entity Information [Line Items]
Non-service cost component of net benefit cost	(4.4)	(5.2)	(10.0)	(9.6)
Other	(1.3)	(3.3)	(7.2)	(9.5)
Other expense	(5.7)	(8.5)	(17.2)	(19.1)
Evergy Metro
Entity Information [Line Items]
Non-service cost component of net benefit cost	(6.3)	(5.2)	(13.2)	(10.3)
Other	0.4	(0.6)	(0.1)	(0.5)
Other expense	$ (5.9)	$ (5.8)	$ (13.3)	$ (10.8)