REVENUE (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 1,483.5	$ 1,566.3	$ 3,715.5	$ 3,945.8
Other	34.1	11.3	103.5	70.4
Operating revenues	1,517.6	1,577.6	3,819.0	4,016.2
Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	720.7	742.2	1,821.8	1,913.7
Other	12.9	6.8	42.7	17.6
Operating revenues	733.6	749.0	1,864.5	1,931.3
Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	507.8	563.0	1,268.6	1,379.0
Other	20.7	5.8	59.7	52.2
Operating revenues	528.5	568.8	1,328.3	1,431.2
Residential
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	636.4	653.0	1,515.6	1,536.3
Residential | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	262.9	268.9	627.5	640.4
Residential | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	241.2	249.2	572.2	575.5
Commercial
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	499.5	539.1	1,272.9	1,391.2
Commercial | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	205.2	219.3	511.0	556.4
Commercial | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	213.3	234.1	558.1	613.5
Industrial
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	166.8	175.3	446.7	478.9
Industrial | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	105.7	111.3	284.6	308.5
Industrial | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	36.6	40.8	99.6	106.7
Other retail
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	9.5	16.0	29.2	35.3
Other retail | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	4.4	5.6	13.3	15.8
Other retail | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	2.7	7.0	8.9	12.3
Total electric retail
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	1,312.2	1,383.4	3,264.4	3,441.7
Total electric retail | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	578.2	605.1	1,436.4	1,521.1
Total electric retail | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	493.8	531.1	1,238.8	1,308.0
Wholesale
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	85.0	96.3	195.8	251.7
Wholesale | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	68.7	67.7	168.1	182.5
Wholesale | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	9.7	23.5	16.7	54.7
Transmission
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	80.7	80.4	238.5	233.5
Transmission | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	72.9	67.7	215.2	205.5
Transmission | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	3.5	7.8	10.4	14.0
Industrial steam and other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	5.6	6.2	16.8	18.9
Industrial steam and other | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0.9	1.7	2.1	4.6
Industrial steam and other | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 0.8	$ 0.6	$ 2.7	$ 2.3