RELATED PARTY TRANSACTIONS AND RELATIONSHIPS (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Evergy Metro | Money Pool
Related Party Transaction [Line Items]
Due from (to) related parties	$ 0.0		$ 0.0		$ 0.0
Evergy Metro | Evergy Missouri West Inc
Related Party Transaction [Line Items]
Due from (to) related parties	62.8		62.8		78.7
Evergy Metro | Evergy Missouri West Inc | Operating Expenses and Capital Costs Billed
Related Party Transaction [Line Items]
Related party transaction	36.0	$ 42.2	75.3	$ 84.2
Evergy Metro | Evergy Kansas Central
Related Party Transaction [Line Items]
Due from (to) related parties	5.9		5.9		14.9
Evergy Metro | Evergy Kansas Central | Operating Expenses and Capital Costs Billed
Related Party Transaction [Line Items]
Related party transaction	19.5	44.3	67.6	75.8
Evergy Metro | Evergy
Related Party Transaction [Line Items]
Due from (to) related parties	14.7		14.7		(4.3)
Evergy Metro | Evergy | Income Tax Receivable
Related Party Transaction [Line Items]
Due from (to) related parties	7.1		7.1
Evergy Metro | Evergy | Income Taxes Payable
Related Party Transaction [Line Items]
Due from (to) related parties					(14.1)
Evergy Kansas Central | Evergy Missouri West Inc
Related Party Transaction [Line Items]
Due from (to) related parties	3.0		3.0		3.1
Evergy Kansas Central | Evergy Missouri West Inc | Operating Expenses and Capital Costs Billed
Related Party Transaction [Line Items]
Related party transaction	10.0	6.4	14.3	12.7
Evergy Kansas Central | Evergy Metro
Related Party Transaction [Line Items]
Due from (to) related parties	(5.9)		(5.9)		(14.9)
Evergy Kansas Central | Evergy Metro | Operating Expenses and Capital Costs Billed
Related Party Transaction [Line Items]
Related party transaction	4.5	$ 8.9	19.5	$ 16.3
Evergy Kansas Central | Evergy
Related Party Transaction [Line Items]
Due from (to) related parties	0.6		0.6		6.9
Evergy Kansas Central | Evergy | Income Tax Receivable
Related Party Transaction [Line Items]
Due from (to) related parties	26.6		26.6		37.9
Evergy Kansas Central | Evergy Metro | Subsidiary of Common Parent
Related Party Transaction [Line Items]
Right-of-use assets under operating leases	29.3		29.3		29.5
Lease liability recorded in other current liabilities	0.7		0.7		0.6
Total long-term obligations under operating leases	$ 28.6		$ 28.6		$ 28.9
Jointly Owned Electricity Generation Plant Iatan No 1 And 2 | Evergy Missouri West Inc
Related Party Transaction [Line Items]
Jointly owned utility plant, proportionate ownership share	18.00%		18.00%
Jeffrey Energy Center | Evergy Missouri West Inc
Related Party Transaction [Line Items]
Jointly owned utility plant, proportionate ownership share	8.00%		8.00%
La Cygne Station | Evergy Kansas Central
Related Party Transaction [Line Items]
Jointly owned utility plant, proportionate ownership share	50.00%		50.00%