TAXES - State Tax Reform (Details) - USD ($) $ in Millions			12 Months Ended
	May 01, 2020	Jun. 01, 2018	Dec. 31, 2020
State Tax Reform [Line Items]
Decrease in net deferred income tax liabilities due to tax reform	$ 233.8
Decrease in net deferred income tax liabilities for revaluation of deferred income tax assets and liabilities in rate base	400.4
Decrease in net deferred income tax liabilities for tax gross-up adjustment for ratemaking purposes due to tax reform	31.7
Decrease in unamortized investment tax credits	183.6
Decrease in unamortized investment tax credits for tax gross up adjustment for ratemaking purposes	16.9
Income tax expense from tax reform	13.8
Kansas state statutory income tax rate thru 2020			7.00%
Evergy Kansas Central
State Tax Reform [Line Items]
Decrease in net deferred income tax liabilities due to tax reform	17.6
Decrease in net deferred income tax liabilities for revaluation of deferred income tax assets and liabilities in rate base	293.7
Decrease in net deferred income tax liabilities for tax gross-up adjustment for ratemaking purposes due to tax reform	17.3
Decrease in unamortized investment tax credits	183.6
Decrease in unamortized investment tax credits for tax gross up adjustment for ratemaking purposes	16.9
Income tax expense from tax reform	109.0
Evergy Metro
State Tax Reform [Line Items]
Decrease in net deferred income tax liabilities due to tax reform	152.9	$ 46.6
Decrease in net deferred income tax liabilities for revaluation of deferred income tax assets and liabilities in rate base	106.7	28.8
Decrease in net deferred income tax liabilities for tax gross-up adjustment for ratemaking purposes due to tax reform	14.4	9.9
Income tax expense from tax reform	$ 32.2	$ 15.5