PENSION PLANS AND POST-RETIREMENT BENEFITS - Narrative (Details) $ in Millions	3 Months Ended
Mar. 31, 2021 USD ($)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	$ 27.8
Contributions to plans in next year	107.4
Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions to plans remainder of year	4.0
Evergy Kansas Central \| Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	17.4
Contributions to plans in next year	42.1
Evergy Kansas Central \| Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions to plans remainder of year	0.6
Evergy Metro \| Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	10.4
Contributions to plans in next year	65.3
Evergy Metro \| Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions to plans remainder of year	$ 3.4
Wolf Creek
Defined Benefit Plan Disclosure [Line Items]
Jointly owned utility plant, proportionate ownership share	94.00%
Wolf Creek \| Evergy Kansas South Inc
Defined Benefit Plan Disclosure [Line Items]
Jointly owned utility plant, proportionate ownership share	47.00%
Wolf Creek \| Evergy Metro
Defined Benefit Plan Disclosure [Line Items]
Jointly owned utility plant, proportionate ownership share	47.00%

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Amount of contribution expected to be received by defined benefit plan from employer in next fiscal year following current fiscal year.

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The proportionate share of interest (percent) in a jointly owned utility plant.

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