PENSION PLANS AND POST-RETIREMENT BENEFITS - Fair Values of Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 1,732.8	$ 1,603.4	$ 887.0
Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	239.9	223.3	124.1
Evergy Kansas Central | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	842.1	804.6	887.0
Evergy Kansas Central | Pension Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	515.2	522.0
Evergy Kansas Central | Pension Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	326.9	282.6
Evergy Kansas Central | Pension Benefits | Domestic equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	233.8	215.0
Evergy Kansas Central | Pension Benefits | Domestic equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	150.6	144.7
Evergy Kansas Central | Pension Benefits | Domestic equities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Domestic equities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Domestic equities | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	83.2	70.3
Evergy Kansas Central | Pension Benefits | International equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	162.4	138.7
Evergy Kansas Central | Pension Benefits | International equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	101.5	91.8
Evergy Kansas Central | Pension Benefits | International equities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | International equities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | International equities | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	60.9	46.9
Evergy Kansas Central | Pension Benefits | Bond funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	281.7	296.4
Evergy Kansas Central | Pension Benefits | Bond funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	233.0	255.4
Evergy Kansas Central | Pension Benefits | Bond funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Bond funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Bond funds | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48.7	41.0
Evergy Kansas Central | Pension Benefits | Real estate investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	46.5	44.8
Evergy Kansas Central | Pension Benefits | Real estate investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Real estate investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Real estate investments | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Real estate investments | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	46.5	44.8
Evergy Kansas Central | Pension Benefits | Combination debt/equity/other fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	30.1	30.1
Evergy Kansas Central | Pension Benefits | Combination debt/equity/other fund | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	30.1	30.1
Evergy Kansas Central | Pension Benefits | Combination debt/equity/other fund | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Combination debt/equity/other fund | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Combination debt/equity/other fund | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Alternative investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	78.5	73.6
Evergy Kansas Central | Pension Benefits | Alternative investment funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Alternative investment funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Alternative investment funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Alternative investment funds | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	78.5	73.6
Evergy Kansas Central | Pension Benefits | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9.1	6.0
Evergy Kansas Central | Pension Benefits | Short-term investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Short-term investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Short-term investments | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Pension Benefits | Short-term investments | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9.1	6.0
Evergy Kansas Central | Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	120.5	109.7	124.1
Evergy Kansas Central | Post-Retirement Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.1	0.2
Evergy Kansas Central | Post-Retirement Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Post-Retirement Benefits | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Post-Retirement Benefits | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	119.4	109.5
Evergy Kansas Central | Post-Retirement Benefits | Domestic equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	40.5	56.4
Evergy Kansas Central | Post-Retirement Benefits | Domestic equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Post-Retirement Benefits | Domestic equities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Post-Retirement Benefits | Domestic equities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Post-Retirement Benefits | Domestic equities | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	40.5	56.4
Evergy Kansas Central | Post-Retirement Benefits | International equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	26.0	14.0
Evergy Kansas Central | Post-Retirement Benefits | International equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Post-Retirement Benefits | International equities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Post-Retirement Benefits | International equities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Post-Retirement Benefits | International equities | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	26.0	14.0
Evergy Kansas Central | Post-Retirement Benefits | Bond funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	52.9	38.4
Evergy Kansas Central | Post-Retirement Benefits | Bond funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Post-Retirement Benefits | Bond funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Post-Retirement Benefits | Bond funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Post-Retirement Benefits | Bond funds | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	52.9	38.4
Evergy Kansas Central | Post-Retirement Benefits | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.7
Evergy Kansas Central | Post-Retirement Benefits | Short-term investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0
Evergy Kansas Central | Post-Retirement Benefits | Short-term investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0
Evergy Kansas Central | Post-Retirement Benefits | Short-term investments | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0
Evergy Kansas Central | Post-Retirement Benefits | Short-term investments | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.7
Evergy Kansas Central | Post-Retirement Benefits | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.1	0.2
Evergy Kansas Central | Post-Retirement Benefits | Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.1	0.2
Evergy Kansas Central | Post-Retirement Benefits | Cash and cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Post-Retirement Benefits | Cash and cash equivalents | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Kansas Central | Post-Retirement Benefits | Cash and cash equivalents | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	890.7	798.8	848.4
Evergy Metro Inc | Pension Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	499.7	450.2
Evergy Metro Inc | Pension Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	149.5	146.9
Evergy Metro Inc | Pension Benefits | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	241.5	201.7
Evergy Metro Inc | Pension Benefits | Domestic equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	244.8	238.1
Evergy Metro Inc | Pension Benefits | Domestic equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	195.3	198.6
Evergy Metro Inc | Pension Benefits | Domestic equities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Domestic equities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Domestic equities | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	49.5	39.5
Evergy Metro Inc | Pension Benefits | International equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	178.7	150.9
Evergy Metro Inc | Pension Benefits | International equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	117.7	104.0
Evergy Metro Inc | Pension Benefits | International equities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | International equities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | International equities | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	61.0	46.9
Evergy Metro Inc | Pension Benefits | Bond funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	71.0	67.4
Evergy Metro Inc | Pension Benefits | Bond funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15.6	19.3
Evergy Metro Inc | Pension Benefits | Bond funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Bond funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Bond funds | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	55.4	48.1
Evergy Metro Inc | Pension Benefits | Real estate investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	50.8	48.2
Evergy Metro Inc | Pension Benefits | Real estate investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12.8	12.6
Evergy Metro Inc | Pension Benefits | Real estate investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Real estate investments | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Real estate investments | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	38.0	35.6
Evergy Metro Inc | Pension Benefits | Combination debt/equity/other fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11.9	13.5
Evergy Metro Inc | Pension Benefits | Combination debt/equity/other fund | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11.9	13.5
Evergy Metro Inc | Pension Benefits | Combination debt/equity/other fund | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Combination debt/equity/other fund | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Combination debt/equity/other fund | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Alternative investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	36.6	31.6
Evergy Metro Inc | Pension Benefits | Alternative investment funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Alternative investment funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Alternative investment funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Alternative investment funds | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	36.6	31.6
Evergy Metro Inc | Pension Benefits | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.0
Evergy Metro Inc | Pension Benefits | Short-term investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0
Evergy Metro Inc | Pension Benefits | Short-term investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0
Evergy Metro Inc | Pension Benefits | Short-term investments | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0
Evergy Metro Inc | Pension Benefits | Short-term investments | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.0
Evergy Metro Inc | Pension Benefits | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	123.9	123.6
Evergy Metro Inc | Pension Benefits | Corporate bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	123.9	123.6
Evergy Metro Inc | Pension Benefits | Corporate bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Corporate bonds | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | U.S. Treasury and agency bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	70.9	69.9
Evergy Metro Inc | Pension Benefits | U.S. Treasury and agency bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	53.5	52.4
Evergy Metro Inc | Pension Benefits | U.S. Treasury and agency bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	17.4	17.5
Evergy Metro Inc | Pension Benefits | U.S. Treasury and agency bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | U.S. Treasury and agency bonds | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Mortgage and asset backed securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.7	5.5
Evergy Metro Inc | Pension Benefits | Mortgage and asset backed securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Mortgage and asset backed securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.7	5.5
Evergy Metro Inc | Pension Benefits | Mortgage and asset backed securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Mortgage and asset backed securities | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	92.9	49.8
Evergy Metro Inc | Pension Benefits | Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	92.9	49.8
Evergy Metro Inc | Pension Benefits | Cash and cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Cash and cash equivalents | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Cash and cash equivalents | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.5	0.3
Evergy Metro Inc | Pension Benefits | Other | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Other | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.5	0.3
Evergy Metro Inc | Pension Benefits | Other | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Pension Benefits | Other | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	119.4	113.6	$ 115.8
Evergy Metro Inc | Post-Retirement Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15.2	10.9
Evergy Metro Inc | Post-Retirement Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	26.8	27.9
Evergy Metro Inc | Post-Retirement Benefits | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	77.4	74.8
Evergy Metro Inc | Post-Retirement Benefits | Domestic equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.2	2.5
Evergy Metro Inc | Post-Retirement Benefits | Domestic equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.2	2.5
Evergy Metro Inc | Post-Retirement Benefits | Domestic equities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | Domestic equities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | Domestic equities | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | International equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.1	0.9
Evergy Metro Inc | Post-Retirement Benefits | International equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.1	0.9
Evergy Metro Inc | Post-Retirement Benefits | International equities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | International equities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | International equities | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | Bond funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	77.5	75.0
Evergy Metro Inc | Post-Retirement Benefits | Bond funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.2
Evergy Metro Inc | Post-Retirement Benefits | Bond funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | Bond funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | Bond funds | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	77.4	74.8
Evergy Metro Inc | Post-Retirement Benefits | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	17.8	17.4
Evergy Metro Inc | Post-Retirement Benefits | Corporate bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | Corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	17.8	17.4
Evergy Metro Inc | Post-Retirement Benefits | Corporate bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | Corporate bonds | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | U.S. Treasury and agency bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11.5	10.3
Evergy Metro Inc | Post-Retirement Benefits | U.S. Treasury and agency bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4.1	2.6
Evergy Metro Inc | Post-Retirement Benefits | U.S. Treasury and agency bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7.4	7.7
Evergy Metro Inc | Post-Retirement Benefits | U.S. Treasury and agency bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | U.S. Treasury and agency bonds | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | Mortgage and asset backed securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.3	2.5
Evergy Metro Inc | Post-Retirement Benefits | Mortgage and asset backed securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | Mortgage and asset backed securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.3	2.5
Evergy Metro Inc | Post-Retirement Benefits | Mortgage and asset backed securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | Mortgage and asset backed securities | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.7	4.7
Evergy Metro Inc | Post-Retirement Benefits | Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.7	4.7
Evergy Metro Inc | Post-Retirement Benefits | Cash and cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | Cash and cash equivalents | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | Cash and cash equivalents | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.3	0.3
Evergy Metro Inc | Post-Retirement Benefits | Other | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | Other | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.3	0.3
Evergy Metro Inc | Post-Retirement Benefits | Other | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Evergy Metro Inc | Post-Retirement Benefits | Other | Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0.0	$ 0.0