PENSION PLANS AND POST-RETIREMENT BENEFITS - APBO (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
ABO for all defined benefit pension plans	$ 2,229.1	$ 2,534.1
Pension plans with the PBO in excess of plan assets
Projected benefit obligation	2,561.7	2,901.1
Fair value of plan assets	1,714.7	1,799.1
Other post-retirement benefit plans with the APBO in excess of plan assets
Accumulated benefit obligation	2,229.1	2,534.1
Fair value of plan assets	1,714.7	1,799.1
Post-Retirement Benefits
Other post-retirement benefit plans with the APBO in excess of plan assets
Accumulated benefit obligation	258.4	280.4
Fair value of plan assets	242.3	248.3
Evergy Kansas Central | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
ABO for all defined benefit pension plans	1,124.2	1,281.6
Pension plans with the PBO in excess of plan assets
Projected benefit obligation	1,264.4	1,429.6
Fair value of plan assets	835.7	887.0
Other post-retirement benefit plans with the APBO in excess of plan assets
Accumulated benefit obligation	1,124.2	1,281.6
Fair value of plan assets	835.7	887.0
Evergy Kansas Central | Post-Retirement Benefits
Other post-retirement benefit plans with the APBO in excess of plan assets
Accumulated benefit obligation	133.9	146.8
Fair value of plan assets	124.0	125.8
Evergy Metro | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
ABO for all defined benefit pension plans	1,081.1	1,227.4
Pension plans with the PBO in excess of plan assets
Projected benefit obligation	1,273.5	1,446.5
Fair value of plan assets	879.0	912.1
Other post-retirement benefit plans with the APBO in excess of plan assets
Accumulated benefit obligation	1,081.1	1,227.4
Fair value of plan assets	879.0	912.1
Evergy Metro | Post-Retirement Benefits
Other post-retirement benefit plans with the APBO in excess of plan assets
Accumulated benefit obligation	124.5	133.6
Fair value of plan assets	$ 118.3	$ 122.5