RECEIVABLES - Allowance for Credit Loses (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance January 1	$ 19.3	$ 10.5
Credit loss expense	7.6	15.5
Write-offs	(17.1)	(20.8)
Recoveries of prior write-offs	9.2	10.0
Ending balance September 30	19.0	15.2
Evergy Kansas Central
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance January 1	7.5	3.8
Credit loss expense	3.2	6.9
Write-offs	(6.9)	(7.3)
Recoveries of prior write-offs	3.5	2.1
Ending balance September 30	7.3	5.5
Evergy Metro
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance January 1	8.1	4.6
Credit loss expense	2.8	5.5
Write-offs	(6.9)	(8.9)
Recoveries of prior write-offs	4.0	5.3
Ending balance September 30	$ 8.0	$ 6.5