REVENUE (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									$ 5,019.6	$ 4,224.0
Other									128.2	51.9
Operating revenues	$ 1,131.6	$ 1,577.6	$ 1,221.7	$ 1,216.9	$ 1,199.8	$ 1,582.5	$ 893.4	$ 600.2	5,147.8	4,275.9	$ 2,571.0
Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									2,444.3	2,606.6
Other									63.1	8.3
Operating revenues	576.1	749.0	585.5	596.8	599.0	764.8	650.9	600.2	2,507.4	2,614.9	2,571.0
Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									1,742.9	1,752.0
Other									63.6	71.1
Operating revenues	$ 375.3	$ 568.8	$ 437.0	$ 425.4	$ 414.2	$ 559.6	$ 452.2	$ 397.1	1,806.5	1,823.1	$ 1,890.7
Residential
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									1,908.1	1,578.8
Residential | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									793.9	846.4
Residential | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									712.4	735.6
Commercial
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									1,781.6	1,356.4
Commercial | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									709.1	702.8
Commercial | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									786.1	794.8
Industrial
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									621.6	527.8
Industrial | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									401.3	396.4
Industrial | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									136.9	138.8
Other retail
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									47.1	30.6
Other retail | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									21.0	20.0
Other retail | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									16.3	10.4
Total electric retail
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									4,358.4	3,493.6
Total electric retail | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									1,925.3	1,965.6
Total electric retail | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									1,651.7	1,679.6
Wholesale
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									327.5	404.4
Wholesale | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									239.9	346.1
Wholesale | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									70.9	53.5
Transmission
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									309.2	308.1
Transmission | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									273.3	288.9
Transmission | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									17.5	14.5
Industrial steam and other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									24.5	17.9
Industrial steam and other | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									5.8	6.0
Industrial steam and other | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									$ 2.8	$ 4.4