PROPERTY, PLANT AND EQUIPMENT - Depreciation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 786.3	$ 567.9	$ 350.0
Variable Interest Entities
Property, Plant and Equipment [Line Items]
Depreciation expense	7.1	7.1	8.3
Evergy Kansas Central
Property, Plant and Equipment [Line Items]
Depreciation expense	425.8	371.3	350.0
Evergy Metro
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 262.7	$ 235.3	$ 228.4