FAIR VALUE MEASUREMENTS - Long-Term Debt (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Book Value | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	$ 12,469.9	$ 11,853.3
Fair Value | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	11,511.4	11,044.9
Evergy Kansas Central | Book Value | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	4,581.0	4,580.4
Evergy Kansas Central | Fair Value | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	4,100.7	4,176.6
Evergy Metro | Book Value | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	3,217.6	2,924.4
Evergy Metro | Fair Value | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	2,987.7	2,738.8
Long-Term debt fair value adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt gross	$ 85.7	$ 87.0