FAIR VALUE MEASUREMENTS - NAV (Details) $ in Millions	6 Months Ended
	Jun. 30, 2020 USD ($) fund extension	Dec. 31, 2019 USD ($)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unfunded Commitments	$ 2.6	$ 3.3
Evergy Kansas Central | Alternative investments fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unfunded Commitments	0.0	0.0
Evergy Kansas Central | Real estate securities fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unfunded Commitments	0.0	0.0
Evergy Kansas Central | Nuclear decommissioning trust:
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	37.8
Unfunded Commitments	2.6	3.3
Evergy Kansas Central | Core bond fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unfunded Commitments	0.0	0.0
Evergy Kansas Central | Combination debt/equity/other fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unfunded Commitments	0.0	0.0
Evergy Kansas Central | Rabbi trust:
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unfunded Commitments	0.0	0.0
Other Evergy
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unfunded Commitments	0.0	0.0
Domestic | Evergy Kansas Central | Equity securities
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unfunded Commitments	$ 2.6	3.3
NAV, number of funds | fund	5
NAV, number of funds making distributions | fund	3
Domestic | Evergy Kansas Central | Equity Securities - Fourth Fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Length of settlement	15 years
NAV, number of extensions | extension	3
NAV, extension term	1 year
Domestic | Evergy Kansas Central | Equity Securities - Fifth Fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Length of settlement	15 years
Fair Value, Measurements, Recurring
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	$ 557.4	573.2
Total rabbi trust	45.1	45.5
Total Assets	613.3	628.6
Fair Value, Measurements, Recurring | Evergy Kansas Central
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	263.2	272.5
Total rabbi trust	31.5	31.7
Total Assets	294.7	304.2
Fair Value, Measurements, Recurring | Evergy Kansas Central | Alternative investments fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	17.4	23.9
Fair Value, Measurements, Recurring | Evergy Kansas Central | Real estate securities fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	12.9	12.6
Fair Value, Measurements, Recurring | Evergy Kansas Central | Core bond fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	39.7	39.3
Total rabbi trust	25.0	25.3
Fair Value, Measurements, Recurring | Evergy Kansas Central | Combination debt/equity/other fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	16.9	16.4
Total rabbi trust	6.4	6.3
Fair Value, Measurements, Recurring | Other Evergy
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total rabbi trust	13.6	13.8
Fair Value, Measurements, Recurring | Domestic | Evergy Kansas Central | Equity securities
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	85.2	86.1
NAV | Fair Value, Measurements, Recurring
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	37.8	44.0
Total rabbi trust	44.4	44.9
Total Assets	82.2	88.9
NAV | Fair Value, Measurements, Recurring | Evergy Kansas Central
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	37.8	44.0
Total rabbi trust	31.4	31.6
Total Assets	69.2	75.6
NAV | Fair Value, Measurements, Recurring | Evergy Kansas Central | Alternative investments fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	$ 17.4	23.9
Length of Settlement	65 days
NAV | Fair Value, Measurements, Recurring | Evergy Kansas Central | Real estate securities fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	$ 12.9	12.6
Length of Settlement	65 days
NAV | Fair Value, Measurements, Recurring | Evergy Kansas Central | Nuclear decommissioning trust:
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust		44.0
NAV | Fair Value, Measurements, Recurring | Evergy Kansas Central | Core bond fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	$ 0.0	0.0
Total rabbi trust	25.0	25.3
NAV | Fair Value, Measurements, Recurring | Evergy Kansas Central | Combination debt/equity/other fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	0.0	0.0
Total rabbi trust	6.4	6.3
NAV | Fair Value, Measurements, Recurring | Evergy Kansas Central | Rabbi trust:
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total rabbi trust	31.4	31.6
NAV | Fair Value, Measurements, Recurring | Other Evergy
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total rabbi trust	13.0	13.3
NAV | Fair Value, Measurements, Recurring | Domestic | Evergy Kansas Central | Equity securities
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	$ 7.5	$ 7.5