RECEIVABLES - Allowance for Credit Loses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance January 1	$ 10.5	$ 9.2
Credit loss expense	24.9	27.2
Write-offs	(28.6)	(38.3)
Recoveries of prior write-offs	12.5	12.4
Ending balance December 31	19.3	10.5
Evergy Kansas Central
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance January 1	3.8	3.9
Credit loss expense	11.1	7.2
Write-offs	(10.0)	(10.7)
Recoveries of prior write-offs	2.6	3.4
Ending balance December 31	7.5	3.8
Evergy Metro
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance January 1	4.6	3.8
Credit loss expense	9.0	13.7
Write-offs	(12.4)	(19.2)
Recoveries of prior write-offs	6.9	6.3
Ending balance December 31	$ 8.1	$ 4.6