REVENUE (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 1,146.1	$ 1,194.4	$ 2,232.0	$ 2,379.5
Other	38.6	27.3	69.4	59.1
Operating revenues	1,184.7	1,221.7	2,301.4	2,438.6
Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	558.9	579.2	1,101.1	1,171.5
Other	11.9	6.3	29.8	10.8
Operating revenues	570.8	585.5	1,130.9	1,182.3
Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	397.4	413.1	760.8	816.0
Other	26.9	23.9	39.0	46.4
Operating revenues	424.3	437.0	799.8	862.4
Residential
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	476.7	431.6	879.2	883.3
Residential | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	196.8	179.2	364.6	371.5
Residential | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	183.6	162.1	331.0	326.3
Commercial
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	388.7	438.6	773.4	852.1
Commercial | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	154.7	172.8	305.8	337.1
Commercial | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	172.7	195.6	344.8	379.4
Industrial
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	139.3	156.6	279.9	303.6
Industrial | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	86.8	98.8	178.9	197.2
Industrial | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	32.9	36.2	63.0	65.9
Other retail
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	9.1	9.5	19.7	19.3
Other retail | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	4.2	5.1	8.9	10.2
Other retail | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	2.7	2.7	6.2	5.3
Total electric retail
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	1,013.8	1,036.3	1,952.2	2,058.3
Total electric retail | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	442.5	455.9	858.2	916.0
Total electric retail | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	391.9	396.6	745.0	776.9
Wholesale
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	47.3	72.3	110.8	155.4
Wholesale | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	44.6	53.5	99.4	114.8
Wholesale | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0.2	13.1	7.0	31.2
Transmission
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	82.2	76.4	157.8	153.1
Transmission | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	74.1	68.6	142.3	137.8
Transmission | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	3.8	3.1	6.9	6.2
Industrial steam and other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	2.8	9.4	11.2	12.7
Industrial steam and other | Evergy Kansas Central
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	(2.3)	1.2	1.2	2.9
Industrial steam and other | Evergy Metro
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 1.5	$ 0.3	$ 1.9	$ 1.7