PENSION PLANS AND POST-RETIREMENT BENEFITS - Narrative (Details) $ in Millions	9 Months Ended
Sep. 30, 2020 USD ($)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	$ 54.3
Contributions to plans remainder of year	78.4
Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	0.6
Contributions to plans remainder of year	3.1
Evergy Kansas Central \| Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	45.7
Evergy Kansas Central \| Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	0.3
Contributions to plans remainder of year	0.4
Evergy Metro \| Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	8.6
Contributions to plans remainder of year	78.4
Evergy Metro \| Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	0.3
Contributions to plans remainder of year	$ 2.7
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 contributions expected to be received by defined benefit plan from employer in fiscal year. Excludes contributions paid by employer in current fiscal year.

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

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