SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property, Plant and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Depreciation rates average	3.00%
Regulatory assets	$ 2,074.4	$ 1,972.2
Depreciation expense reflected in retail rates	$ 9.0
Minimum
Property, Plant and Equipment [Line Items]
Generating facilities	8 years
Transmission facilities	15 years
Distribution facilities	8 years
Other	5 years
Maximum
Property, Plant and Equipment [Line Items]
Generating facilities	87 years
Transmission facilities	94 years
Distribution facilities	73 years
Other	84 years
Evergy Kansas Central
Property, Plant and Equipment [Line Items]
Regulatory assets	$ 896.3	823.7
Evergy Kansas Central \| Minimum
Property, Plant and Equipment [Line Items]
Generating facilities	8 years
Transmission facilities	36 years
Distribution facilities	19 years
Other	7 years
Evergy Kansas Central \| Maximum
Property, Plant and Equipment [Line Items]
Generating facilities	87 years
Transmission facilities	94 years
Distribution facilities	73 years
Other	84 years
Evergy Metro
Property, Plant and Equipment [Line Items]
Regulatory assets	$ 615.5	559.8
Evergy Metro \| Minimum
Property, Plant and Equipment [Line Items]
Generating facilities	20 years
Transmission facilities	15 years
Distribution facilities	8 years
Other	5 years
Evergy Metro \| Maximum
Property, Plant and Equipment [Line Items]
Generating facilities	60 years
Transmission facilities	70 years
Distribution facilities	55 years
Other	50 years
Retired Generation Facilities
Property, Plant and Equipment [Line Items]
Regulatory assets	$ 128.4	130.5
Retired Generation Facilities \| Evergy Kansas Central
Property, Plant and Equipment [Line Items]
Regulatory assets	0.0	0.0
Retired Generation Facilities \| Evergy Metro
Property, Plant and Equipment [Line Items]
Regulatory assets	$ 0.0	$ 0.0

The expense charged against earnings during the period to allocate the capitalized costs of regulatory assets over the periods expected to benefit from such costs.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

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+ References

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Composite depreciation rate for public utility plants in service.

+ References

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- Definition

Useful life of utility distribution assets owned by public utility, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Useful life of utility generation assets owned by public utility, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Useful life of other property, plant and equipment (PPE) owned by public utility, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Useful life of utility transmission equipment owned by public utility, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

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