RECEIVABLES - Allowance for Credit Loses (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance January 1	$ 10.5	$ 9.2
Credit loss expense	11.6	10.6
Write-offs	(10.9)	(16.6)
Recoveries of prior write-offs	6.8	6.0
Ending balance June 30	18.0	9.2
Evergy Kansas Central
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance January 1	3.8	3.9
Credit loss expense	2.9	3.4
Write-offs	(3.3)	(5.3)
Recoveries of prior write-offs	1.5	1.8
Ending balance June 30	4.9	3.8
Evergy Metro
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance January 1	4.6	3.8
Credit loss expense	5.7	4.9
Write-offs	(5.0)	(7.7)
Recoveries of prior write-offs	3.7	2.9
Ending balance June 30	$ 9.0	$ 3.9