TAXES - Income Tax Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Current income taxes
Federal	$ (21.0)	$ 8.7	$ (18.6)	$ 20.6
State	(6.9)	(0.2)	(7.3)	(0.8)
Total	(27.9)	8.5	(25.9)	19.8
Deferred income taxes
Federal	30.8	9.8	36.8	2.5
State	33.4	7.2	36.2	13.5
Total	64.2	17.0	73.0	16.0
Investment tax credit amortization	(2.6)	(1.1)	(3.3)	(2.1)
Income tax expense	$ 33.7	$ 24.4	$ 43.8	$ 33.7
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax rate	21.00%	21.00%	21.00%	21.00%
Effect of:
COLI policies	(1.60%)	(1.80%)	(1.60%)	(1.80%)
State income taxes	3.60%	2.90%	3.20%	3.60%
Flow through depreciation for plant-related differences	(5.00%)	(2.70%)	(4.70%)	(3.40%)
Federal tax credits	(4.60%)	(4.00%)	(4.60%)	(3.90%)
Non-controlling interest	(0.30%)	(0.50%)	(0.30%)	(0.40%)
AFUDC equity	(0.70%)	(0.10%)	(0.60%)	0.00%
Amortization of federal investment tax credits	(0.50%)	(0.50%)	(0.50%)	(0.50%)
State tax rate change	8.10%	0.00%	5.50%	0.00%
Valuation allowance	0.00%	0.00%	0.00%	(2.80%)
Stock compensation	(0.40%)	(0.30%)	(0.20%)	(0.10%)
Officer compensation limitation	0.20%	0.10%	0.20%	0.10%
Other	0.00%	0.40%	0.00%	0.20%
Effective income tax rate	19.80%	14.50%	17.40%	12.00%
Evergy Kansas Central
Current income taxes
Federal	$ (12.1)	$ 17.5	$ 12.1	$ 27.9
State	(6.5)	(1.6)	(6.9)	(1.2)
Total	(18.6)	15.9	5.2	26.7
Deferred income taxes
Federal	(10.4)	(10.7)	(28.6)	(13.9)
State	150.2	5.5	152.8	9.1
Total	139.8	(5.2)	124.2	(4.8)
Investment tax credit amortization	(2.3)	(0.8)	(2.7)	(1.5)
Income tax expense	$ 118.9	$ 9.9	$ 126.7	$ 20.4
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax rate	21.00%	21.00%	21.00%	21.00%
Effect of:
COLI policies	(3.00%)	(3.30%)	(3.00%)	(3.30%)
State income taxes	4.40%	3.00%	3.60%	4.00%
Flow through depreciation for plant-related differences	0.10%	0.30%	0.00%	0.10%
Federal tax credits	(6.90%)	(6.10%)	(6.80%)	(6.10%)
Non-controlling interest	(0.60%)	(1.00%)	(0.60%)	(0.80%)
AFUDC equity	(1.60%)	(0.10%)	(1.10%)	(0.10%)
Amortization of federal investment tax credits	(0.70%)	(0.70%)	(0.70%)	(0.70%)
State tax rate change	134.00%	0.00%	75.60%	0.00%
Valuation allowance	0.00%	0.00%	0.00%	(1.00%)
Stock compensation	(0.50%)	(0.50%)	(0.30%)	(0.30%)
Other	0.00%	0.30%	0.10%	0.30%
Effective income tax rate	146.20%	12.90%	87.80%	13.10%
Evergy Metro
Current income taxes
Federal	$ (11.1)	$ 26.4	$ 0.5	$ 34.3
State	(0.2)	4.6	1.0	5.4
Total	(11.3)	31.0	1.5	39.7
Deferred income taxes
Federal	26.2	(19.7)	16.7	(24.9)
State	(37.3)	(3.0)	(37.7)	(2.6)
Total	(11.1)	(22.7)	(21.0)	(27.5)
Investment tax credit amortization	(0.2)	(0.3)	(0.5)	(0.5)
Income tax expense	$ (22.6)	$ 8.0	$ (20.0)	$ 11.7
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax rate	21.00%	21.00%	21.00%	21.00%
Effect of:
COLI policies	(0.30%)	(0.10%)	(0.20%)	(0.10%)
State income taxes	3.30%	1.80%	3.00%	2.50%
Flow through depreciation for plant-related differences	(9.50%)	(5.70%)	(9.00%)	(6.00%)
Federal tax credits	(2.40%)	(1.50%)	(2.40%)	(1.50%)
AFUDC equity	0.10%	0.00%	0.00%	0.00%
Amortization of federal investment tax credits	(0.40%)	(0.30%)	(0.40%)	(0.30%)
State tax rate change	(40.10%)	0.00%	(29.70%)	0.00%
Stock compensation	(0.30%)	(0.20%)	(1.10%)	0.10%
Officer compensation limitation	0.60%	0.30%	0.40%	0.30%
Other	(0.10%)	(3.30%)	0.00%	(2.50%)
Effective income tax rate	(28.10%)	12.00%	(18.40%)	13.50%