ORGANIZATION AND BASIS OF PRESENTATION - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Income
Net income	$ 136.3	$ 72.2	$ 144.6	$ 103.4	$ 208.5	$ 248.0
Less: Net income attributable to noncontrolling interests	2.9		4.9		5.7	8.8
Net income attributable to Evergy, Inc.	$ 133.4		$ 139.7		$ 202.8	$ 239.2
Common Shares Outstanding
Weighted average equivalent common shares outstanding - basic (in shares)	227.2		243.2		227.1	248.0
Add: effect of dilutive securities (in shares)	0.4		0.2		0.5	0.2
Diluted average number of common shares outstanding (in shares)	227.6		243.4		227.6	248.2
Basic and diluted earnings per common share (in dollars per share)	$ 0.59		$ 0.57		$ 0.89	$ 0.96