TAXES - Income Tax Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Current income taxes
Federal	$ (16.4)	$ (31.2)	$ (35.0)	$ (10.6)
State	(0.4)	(0.8)	(7.7)	(1.6)
Total	(16.8)	(32.0)	(42.7)	(12.2)
Deferred income taxes
Federal	46.6	75.5	83.4	78.0
State	21.5	23.0	57.7	36.5
Total	68.1	98.5	141.1	114.5
Investment tax credit amortization	(1.3)	(1.0)	(4.6)	(3.1)
Income tax expense	$ 50.0	$ 65.5	$ 93.8	$ 99.2
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%)	(1.60%)	(1.60%)	(1.70%)
State income taxes	3.50%	4.00%	3.40%	3.90%
Flow through depreciation for plant-related differences	(4.90%)	(3.10%)	(4.80%)	(3.20%)
Federal tax credits	(4.60%)	(3.90%)	(4.60%)	(3.90%)
Non-controlling interest	(0.30%)	(0.40%)	(0.30%)	(0.40%)
AFUDC equity	(0.20%)	0.00%	(0.30%)	0.00%
Amortization of federal investment tax credits	(0.70%)	(0.50%)	(0.70%)	(0.50%)
Changes In Uncertain Tax Positions, Net	0.00%	(0.40%)	0.00%	(0.30%)
State tax rate change	0.00%	0.00%	2.00%	0.00%
Valuation allowance	(0.40%)	0.00%	(0.20%)	(1.10%)
Stock compensation	0.00%	0.30%	(0.10%)	0.20%
Officer compensation limitation	0.20%	0.10%	0.20%	0.10%
Other	0.00%	(0.50%)	0.00%	(0.30%)
Effective income tax rate	12.00%	15.00%	14.00%	13.80%
Evergy Kansas Central
Current income taxes
Federal	$ (4.6)	$ 11.2	$ 7.5	$ 39.1
State	(6.4)	(1.2)	(13.3)	(2.4)
Total	(11.0)	10.0	(5.8)	36.7
Deferred income taxes
Federal	17.9	4.6	(10.7)	(9.3)
State	16.6	12.0	169.4	21.1
Total	34.5	16.6	158.7	11.8
Investment tax credit amortization	(1.0)	(0.8)	(3.7)	(2.3)
Income tax expense	$ 22.5	$ 25.8	$ 149.2	$ 46.2
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax rate	21.00%	21.00%	21.00%	21.00%
Effect of:
COLI policies	(2.90%)	(2.80%)	(2.90%)	(3.00%)
State income taxes	2.30%	4.40%	2.90%	4.20%
Flow through depreciation for plant-related differences	(0.40%)	0.80%	(0.20%)	0.50%
Federal tax credits	(6.80%)	(6.20%)	(6.80%)	(6.10%)
Non-controlling interest	(0.70%)	(0.80%)	(0.60%)	(0.80%)
AFUDC equity	0.10%	(0.10%)	(0.40%)	(0.10%)
Amortization of federal investment tax credits	(1.10%)	(0.70%)	(1.00%)	(0.70%)
Changes In Uncertain Tax Positions, Net	0.00%	(0.90%)	0.00%	(0.50%)
State tax rate change	0.00%	0.00%	32.00%	0.00%
Valuation allowance	0.00%	0.00%	0.00%	(0.50%)
Stock compensation	0.00%	0.00%	(0.10%)	(0.10%)
Other	0.00%	(1.40%)	0.00%	(0.70%)
Effective income tax rate	11.50%	13.30%	43.90%	13.20%
Evergy Metro
Current income taxes
Federal	$ (8.9)	$ (2.2)	$ (8.4)	$ 32.1
State	9.5	3.9	10.5	9.3
Total	0.6	1.7	2.1	41.4
Deferred income taxes
Federal	22.2	26.3	38.9	1.4
State	2.6	4.5	(35.1)	1.9
Total	24.8	30.8	3.8	3.3
Investment tax credit amortization	(0.3)	(0.3)	(0.8)	(0.8)
Income tax expense	$ 25.1	$ 32.2	$ 5.1	$ 43.9
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax rate	21.00%	21.00%	21.00%	21.00%
Effect of:
COLI policies	(0.20%)	(0.10%)	(0.20%)	(0.10%)
State income taxes	5.50%	3.60%	4.50%	3.20%
Flow through depreciation for plant-related differences	(9.10%)	(6.10%)	(9.10%)	(6.10%)
Federal tax credits	(2.40%)	(1.30%)	(2.40%)	(1.40%)
AFUDC equity	(0.50%)	0.00%	(0.30%)	0.00%
Amortization of federal investment tax credits	(0.40%)	(0.30%)	(0.40%)	(0.30%)
State tax rate change	0.00%	0.00%	(11.40%)	0.00%
Stock compensation	0.00%	0.00%	(0.40%)	0.00%
Officer compensation limitation	0.50%	0.30%	0.50%	0.30%
Other	0.10%	0.40%	0.00%	(0.40%)
Effective income tax rate	14.50%	17.50%	1.80%	16.20%