RECEIVABLES - Allowance for Credit Loses (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance January 1	$ 19.3	$ 10.5
Credit loss expense	2.4	11.6
Write-offs	(8.2)	(10.9)
Recoveries of prior write-offs	6.5	6.8
Ending balance June 30	20.0	18.0
Evergy Kansas Central
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance January 1	7.5	3.8
Credit loss expense	0.4	2.9
Write-offs	(2.7)	(3.3)
Recoveries of prior write-offs	2.4	1.5
Ending balance June 30	7.6	4.9
Evergy Metro
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance January 1	8.1	4.6
Credit loss expense	1.3	5.7
Write-offs	(3.7)	(5.0)
Recoveries of prior write-offs	3.0	3.7
Ending balance June 30	$ 8.7	$ 9.0