Guarantees (Details) $ in Millions	Mar. 31, 2016 USD ($)
Guarantees
Total guarantees	$ 266.1
Guarantees expiring in less than 1 year	139.2
Guarantees expiring within 1 to 3 years	9.5
Guarantees with expiration over 3 years	117.4
Guarantees supporting commodity transactions of subsidiaries
Guarantees
Total guarantees	168.7
Guarantees expiring in less than 1 year	89.7
Guarantees expiring within 1 to 3 years	0.0
Guarantees with expiration over 3 years	79.0
Guarantees supporting commodity transactions of subsidiaries \| WBS
Guarantees
Total guarantees	5.0
Guarantees supporting commodity transactions of subsidiaries \| PDL
Guarantees
Total guarantees	11.0
Guarantees supporting commodity transactions of subsidiaries \| MERC
Guarantees
Total guarantees	114.8
Guarantees supporting commodity transactions of subsidiaries \| MGU
Guarantees
Total guarantees	37.9
Standby letters of credit
Guarantees
Total guarantees	28.3
Guarantees expiring in less than 1 year	18.7
Guarantees expiring within 1 to 3 years	9.4
Guarantees with expiration over 3 years	0.2
Surety bonds
Guarantees
Total guarantees	10.2
Guarantees expiring in less than 1 year	10.2
Guarantees expiring within 1 to 3 years	0.0
Guarantees with expiration over 3 years	0.0
Other guarantees
Guarantees
Total guarantees	58.9
Guarantees expiring in less than 1 year	20.6
Guarantees expiring within 1 to 3 years	0.1
Guarantees with expiration over 3 years	38.2
Other guarantees \| PDL
Guarantees
Total guarantees	19.0
Other guarantees \| WPS
Guarantees
Total guarantees	20.0
Other guarantees \| Integrys
Guarantees
Total guarantees	10.0
Reciprocal guarantee \| PDL
Guarantees
Total guarantees	6.6
Other indemnifications
Guarantees
Total guarantees	9.9
Liability related to workers compensation coverage	$ 9.2

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

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

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

- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

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

- Definition

Represents the maximum potential payments with respect to the entity's guarantees that expire in less than a year.

+ References

No definition available.

+ Details

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Namespace Prefix:	wec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the maximum potential payments with respect to the entity's guarantees that expire after three years.

+ References

No definition available.

+ Details

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Namespace Prefix:	wec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the maximum potential payments with respect to the entity's guarantees that expire within one to three years.

+ References

No definition available.

+ Details

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Namespace Prefix:	wec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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- Details

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- Details

Name:	dei_LegalEntityAxis=wec_WPSPowerDevelopmentLLCMember
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- Details

Name:	dei_LegalEntityAxis=wec_MERCMember
Namespace Prefix:
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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=wec_ThirdPartyReciprocalGuaranteeMember
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- Details

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