XML 87 R67.htm IDEA: XBRL DOCUMENT v3.19.1

FAIR VALUE MEASUREMENTS - NAV (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) fund extension	Dec. 31, 2018 USD ($)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unfunded Commitments	$ 4.0	$ 4.3
Westar Energy | Alternative investments fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unfunded Commitments	$ 0.0	0.0
Length of Settlement	65 days
Westar Energy | Real estate securities fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unfunded Commitments	$ 0.0	0.0
Length of Settlement	65 days
Westar Energy | Nuclear decommissioning trust:
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	$ 41.8
Unfunded Commitments	4.0	4.3
Westar Energy | Core bond fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unfunded Commitments	0.0	0.0
Westar Energy | Combination debt/equity/other fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unfunded Commitments	0.0	0.0
Westar Energy | Rabbi trust:
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unfunded Commitments	0.0	0.0
Other Evergy
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unfunded Commitments	0.0	0.0
Domestic | Westar Energy | Equity securities
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unfunded Commitments	$ 4.0	4.3
NAV, Number of funds | fund	5
NAV, Number of funds making distributions | fund	3
Domestic | Westar Energy | Equity Securities - Fourth Fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Length of Settlement	15 years
NAV, Extension term	1 year
NAV, Number of extensions | extension	3
Domestic | Westar Energy | Equity Securities - Fifth Fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Length of Settlement	15 years
Fair Value, Measurements, Recurring
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	$ 518.3	472.1
Total rabbi trust	44.6	43.8
Total Assets	575.5	528.3
Fair Value, Measurements, Recurring | Westar Energy
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	248.4	227.5
Total rabbi trust	31.1	30.6
Total Assets	279.5	258.1
Fair Value, Measurements, Recurring | Westar Energy | Alternative investments fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	23.3	24.1
Fair Value, Measurements, Recurring | Westar Energy | Real estate securities fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	12.0	11.8
Fair Value, Measurements, Recurring | Westar Energy | Core bond fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	34.6	37.5
Total rabbi trust	24.7	24.8
Fair Value, Measurements, Recurring | Westar Energy | Combination debt/equity/other fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	14.7	12.9
Total rabbi trust	6.2	5.6
Fair Value, Measurements, Recurring | Other Evergy
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total rabbi trust	13.5	13.2
Fair Value, Measurements, Recurring | Domestic | Westar Energy | Equity securities
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	80.1	70.6
NAV | Fair Value, Measurements, Recurring
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	41.8	42.6
Total rabbi trust	44.0	43.6
Total Assets	85.8	86.2
NAV | Fair Value, Measurements, Recurring | Westar Energy
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	41.8	42.6
Total rabbi trust	30.9	30.4
Total Assets	72.7	73.0
NAV | Fair Value, Measurements, Recurring | Westar Energy | Alternative investments fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	23.3	24.1
NAV | Fair Value, Measurements, Recurring | Westar Energy | Real estate securities fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	12.0	11.8
NAV | Fair Value, Measurements, Recurring | Westar Energy | Nuclear decommissioning trust:
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust		42.6
NAV | Fair Value, Measurements, Recurring | Westar Energy | Core bond fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	0.0	0.0
Total rabbi trust	24.7	24.8
NAV | Fair Value, Measurements, Recurring | Westar Energy | Combination debt/equity/other fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	0.0	0.0
Total rabbi trust	6.2	5.6
NAV | Fair Value, Measurements, Recurring | Westar Energy | Rabbi trust:
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total rabbi trust	30.9	30.4
NAV | Fair Value, Measurements, Recurring | Other Evergy
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total rabbi trust	13.1	13.2
NAV | Fair Value, Measurements, Recurring | Domestic | Westar Energy | Equity securities
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	$ 6.5	$ 6.7

X

- Definition

Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Extension Term

+ References

No definition available.

+ Details

Name:	evrg_FairValueInvestmentsEntitiesthatCalculateNetAssetValuePerShareExtensionTerm
Namespace Prefix:	evrg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Number Of Extensions

+ References

No definition available.

+ Details

Name:	evrg_FairValueInvestmentsEntitiesthatCalculateNetAssetValuePerShareNumberOfExtensions
Namespace Prefix:	evrg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Number Of Funds

+ References

No definition available.

+ Details

Name:	evrg_FairValueInvestmentsEntitiesthatCalculateNetAssetValuePerShareNumberOfFunds
Namespace Prefix:	evrg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Number Of Funds Making Distributions

+ References

No definition available.

+ Details

Name:	evrg_FairValueInvestmentsEntitiesthatCalculateNetAssetValuePerShareNumberOfFundsMakingDistributions
Namespace Prefix:	evrg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Rabbi Trust, Fair Value Disclosure

+ References

No definition available.

+ Details

Name:	evrg_RabbiTrustFairValueDisclosure
Namespace Prefix:	evrg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

+ Details

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

The fair value of investments held in a trust fund to pay for the costs of decontaminating and decommissioning facilities, whether such amount is presented as a separate caption or as a parenthetical disclosure on the balance sheet. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

+ 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
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

+ Details

Name:	us-gaap_DecommissioningTrustAssetsAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Estimate remaining period the underlying assets are expected to be liquidated by the investees for investments for which net asset value per share is calculated (including by unit, membership interest, or other ownership interest unit measure), in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=SL6742756-110258

+ Details

Name:	us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareLiquidatingInvestmentRemainingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The amount of unfunded commitments for which the entity is obligated, to those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=SL6742756-110258

+ Details

Name:	us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareUnfundedCommittments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Details

Name:	dei_LegalEntityAxis=evrg_WestarEnergyIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=evrg_AlternativeInvestmentFundMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_RealEstateFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=evrg_DecommissioningTrustAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=evrg_CoreBondFundMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=evrg_DebtEquityOtherFundMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=evrg_RabbiTrustsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	dei_LegalEntityAxis=evrg_OtherEvergyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_GeographicDistributionAxis=us-gaap_GeographicDistributionDomesticMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=evrg_EquitySecuritiesFourthFundMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=evrg_EquitySecuritiesFifthFundMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: