FAIR VALUE MEASUREMENTS - Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trust	$ 768.7	$ 652.1
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trust	48.2	47.8
Fair Value, Measurements, Recurring | NAV
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trust	61.8	43.7
Book Value | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	9,687.2	9,627.3
Book Value | Fair Value, Measurements, Recurring | Variable Interest Entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	0.0	18.8
Fair Value | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	10,758.5	11,274.2
Fair Value | Fair Value, Measurements, Recurring | Level 2 | Variable Interest Entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	0.0	19.1
Evergy Kansas Central | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trust	368.4	309.8
Evergy Kansas Central | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trust	0.0	0.0
Evergy Kansas Central | Fair Value, Measurements, Recurring | NAV
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trust	61.8	43.7
Evergy Kansas Central | Fair Value, Measurements, Recurring | NAV | Nuclear decommissioning trust:
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trust	61.8	43.7
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	3,934.2	3,931.5
Evergy Kansas Central | Book Value | Fair Value, Measurements, Recurring | Variable Interest Entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	0.0	18.8
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	4,522.5	4,801.7
Evergy Kansas Central | Fair Value | Fair Value, Measurements, Recurring | Level 2 | Variable Interest Entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	0.0	19.1
Evergy Metro | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trust	400.3	342.3
Evergy Metro | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trust	48.2	47.8
Evergy Metro | Fair Value, Measurements, Recurring | NAV
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trust	0.0	0.0
Evergy Metro | Book Value | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	2,925.0	2,923.0
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	3,400.8	3,591.2
Long-Term debt fair value adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt gross	97.9	110.4
Long-Term debt fair value adjustment | Evergy Kansas Central
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt gross	0.0	0.0
Long-Term debt fair value adjustment | Evergy Metro
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt gross	$ 0.0	$ 0.0