RECEIVABLES - Allowance for Credit Loses (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance January 1	$ 10.5	$ 9.2
Credit loss expense	15.5	22.4
Write-offs	(20.8)	(31.9)
Recoveries of prior write-offs	10.0	9.2
Ending balance September 30	15.2	8.9
Evergy Kansas Central
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance January 1	3.8	3.9
Credit loss expense	6.9	5.6
Write-offs	(7.3)	(8.8)
Recoveries of prior write-offs	2.1	2.7
Ending balance September 30	5.5	3.4
Evergy Metro
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance January 1	4.6	3.8
Credit loss expense	5.5	11.7
Write-offs	(8.9)	(16.2)
Recoveries of prior write-offs	5.3	4.6
Ending balance September 30	$ 6.5	$ 3.9