TAXES - Income Tax Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Current income taxes
Federal	$ 2.4	$ 11.9
State	(0.4)	(0.6)
Total	2.0	11.3
Deferred income taxes
Federal	6.0	(7.3)
State	2.8	6.3
Total	8.8	(1.0)
Investment tax credit amortization	(0.7)	(1.0)
Income tax expense	$ 10.1	$ 9.3
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax rate	21.00%	21.00%
Effect of:
COLI policies	(1.60%)	(1.80%)
State income taxes	2.30%	4.60%
Flow through depreciation for plant-related differences	(3.90%)	(4.40%)
Federal tax credits	(4.50%)	(3.90%)
Non-controlling interest	(0.30%)	(0.30%)
AFUDC equity	(0.30%)	0.00%
Amortization of federal investment tax credits	(0.50%)	(0.50%)
Valuation allowance	0.00%	(7.00%)
Stock compensation	0.10%	0.10%
Officer compensation limitation	0.10%	0.20%
Other	(0.20%)	0.20%
Effective income tax rate	12.20%	8.20%
Evergy Kansas Central
Current income taxes
Federal	$ 24.2	$ 10.4
State	(0.4)	0.4
Total	23.8	10.8
Deferred income taxes
Federal	(18.2)	(3.2)
State	2.6	3.6
Total	(15.6)	0.4
Investment tax credit amortization	(0.4)	(0.7)
Income tax expense	$ 7.8	$ 10.5
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax rate	21.00%	21.00%
Effect of:
COLI policies	(3.10%)	(3.20%)
State income taxes	2.70%	5.00%
Flow through depreciation for plant-related differences	0.00%	(0.10%)
Federal tax credits	(6.60%)	(6.10%)
Non-controlling interest	(0.60%)	(0.60%)
AFUDC equity	(0.40%)	(0.10%)
Amortization of federal investment tax credits	(0.70%)	(0.70%)
Valuation allowance	0.00%	(2.10%)
Stock compensation	(0.10%)	(0.10%)
Other	0.10%	0.30%
Effective income tax rate	12.30%	13.30%
Evergy Metro
Current income taxes
Federal	$ 11.6	$ 7.9
State	1.2	0.8
Total	12.8	8.7
Deferred income taxes
Federal	(9.5)	(5.2)
State	(0.4)	0.4
Total	(9.9)	(4.8)
Investment tax credit amortization	(0.3)	(0.2)
Income tax expense	$ 2.6	$ 3.7
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax rate	21.00%	21.00%
Effect of:
COLI policies	0.00%	(0.10%)
State income taxes	2.20%	4.90%
Flow through depreciation for plant-related differences	(7.70%)	(7.20%)
Federal tax credits	(2.40%)	(1.50%)
AFUDC equity	(0.20%)	0.00%
Amortization of federal investment tax credits	(0.40%)	(0.30%)
Stock compensation	(3.60%)	1.00%
Officer compensation limitation	0.00%	0.30%
Other	0.40%	0.30%
Effective income tax rate	9.30%	18.40%