ASSET RETIREMENT OBLIGATIONS (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2019
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	$ 687.1	$ 405.1
Liabilities assumed upon merger with Great Plains Energy	0.0	412.2
Liabilities incurred during the year	0.0	7.4
Revision in timing and/or estimates	(22.3)	(150.1)
Settlements	(17.8)	(22.4)
Accretion	27.1	34.9
Ending balance	674.1	687.1
Less: current portion	(71.3)	(49.8)
Total noncurrent asset retirement obligation	602.8	637.3
Evergy Kansas Central
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	281.1	405.1
Liabilities assumed upon merger with Great Plains Energy	0.0	0.0
Liabilities incurred during the year	0.0	7.4
Revision in timing and/or estimates	(12.4)	(138.7)
Settlements	(14.8)	(12.0)
Accretion	19.0	19.3
Ending balance	272.9	281.1
Less: current portion	(23.3)	(17.1)
Total noncurrent asset retirement obligation	249.6	264.0
Evergy Metro
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	261.0	266.3
Liabilities assumed upon merger with Great Plains Energy	0.0	0.0
Liabilities incurred during the year	0.0	0.0
Revision in timing and/or estimates	(9.9)	(11.4)
Settlements	(2.5)	(13.1)
Accretion	5.0	19.2
Ending balance	253.6	261.0
Less: current portion	(36.1)	(29.2)
Total noncurrent asset retirement obligation	$ 217.5	231.8
Wolf Creek Unit
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Revision in timing and/or estimates		$ 127.0
Jointly owned utility plant, proportionate ownership share		47.00%	94.00%	94.00%
Wolf Creek Unit \| Evergy Kansas Central
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Revision in timing and/or estimates		$ 127.0
Jointly owned utility plant, proportionate ownership share		47.00%		47.00%
Wolf Creek Unit \| Evergy Metro
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Jointly owned utility plant, proportionate ownership share			47.00%	47.00%

Asset Retirement Obligation, Liabilities Assumed

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- Definition

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
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Current portion of the carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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Amount of asset retirement obligations incurred during the period.

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Amount of asset retirement obligations settled, or otherwise disposed of, during the period. This may include asset retirement obligations transferred to third parties associated with the sale of a long-lived asset.

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Amount of increase (decrease) in the asset retirement obligation from changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Noncurrent portion of the carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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The proportionate share of interest (percent) in a jointly owned utility plant.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 360
-Section S99
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