XML 134 R118.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Employee Benefits - Plan Assets (Details) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
--- | --- | --- | ---
Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | $ 2,966.8 | $ 2,709.2 | $ 2,755.1
Pension Plan | Level 1, 2, and 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 2,141.9 | 1,343.0 |
Pension Plan | Level 1, 2, and 3 | Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 53.6 | 61.7 |
Pension Plan | Level 1, 2, and 3 | United States equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 345.1 | 274.0 |
Pension Plan | Level 1, 2, and 3 | International equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 352.9 | 54.7 |
Pension Plan | Level 1, 2, and 3 | United States bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 1,031.5 | 862.1 |
Pension Plan | Level 1, 2, and 3 | International bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 104.6 | 75.9 |
Pension Plan | Level 1, 2, and 3 | Private equity and real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 254.2 | 14.6 |
Pension Plan | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 853.5 | 331.7 |
Pension Plan | Level 1 | Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 3.7 |
Pension Plan | Level 1 | United States equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 345.0 | 273.9 |
Pension Plan | Level 1 | International equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 352.1 | 54.1 |
Pension Plan | Level 1 | United States bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 138.6 | 0.0 |
Pension Plan | Level 1 | International bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 17.8 | 0.0 |
Pension Plan | Level 1 | Private equity and real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
Pension Plan | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 1,187.5 | 995.9 |
Pension Plan | Level 2 | Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 53.6 | 58.0 |
Pension Plan | Level 2 | United States equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.1 | 0.1 |
Pension Plan | Level 2 | International equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.6 |
Pension Plan | Level 2 | United States bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 892.9 | 861.3 |
Pension Plan | Level 2 | International bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 86.8 | 75.9 |
Pension Plan | Level 2 | Private equity and real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 154.1 | 0.0 |
Pension Plan | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 100.9 | 15.4 |
Pension Plan | Level 3 | Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
Pension Plan | Level 3 | United States equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
Pension Plan | Level 3 | International equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.8 | 0.0 |
Pension Plan | Level 3 | United States bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.8 |
Pension Plan | Level 3 | International bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
Pension Plan | Level 3 | Private equity and real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 100.1 | 14.6 |
Pension Plan | Investments measured at net asset value per share |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 824.9 | 1,366.2 |
OPEB Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 841.5 | 773.5 | $ 749.8
OPEB Plan | Level 1, 2, and 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 538.1 | 218.2 |
OPEB Plan | Level 1, 2, and 3 | Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 21.9 | 32.2 |
OPEB Plan | Level 1, 2, and 3 | United States equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 101.0 | 34.3 |
OPEB Plan | Level 1, 2, and 3 | International equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 115.5 | 3.7 |
OPEB Plan | Level 1, 2, and 3 | United States bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 269.1 | 137.9 |
OPEB Plan | Level 1, 2, and 3 | International bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 16.3 | 8.8 |
OPEB Plan | Level 1, 2, and 3 | Private equity and real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 14.3 | 1.3 |
OPEB Plan | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 364.1 | 66.6 |
OPEB Plan | Level 1 | Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 19.6 | 28.8 |
OPEB Plan | Level 1 | United States equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 101.0 | 34.3 |
OPEB Plan | Level 1 | International equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 115.3 | 3.5 |
OPEB Plan | Level 1 | United States bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 121.0 | 0.0 |
OPEB Plan | Level 1 | International bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 7.2 | 0.0 |
OPEB Plan | Level 1 | Private equity and real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
OPEB Plan | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 166.1 | 150.3 |
OPEB Plan | Level 2 | Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 2.3 | 3.4 |
OPEB Plan | Level 2 | United States equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
OPEB Plan | Level 2 | International equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.2 |
OPEB Plan | Level 2 | United States bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 148.1 | 137.9 |
OPEB Plan | Level 2 | International bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 9.1 | 8.8 |
OPEB Plan | Level 2 | Private equity and real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 6.6 | 0.0 |
OPEB Plan | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 7.9 | 1.3 |
OPEB Plan | Level 3 | Cash and cash equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
OPEB Plan | Level 3 | United States equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
OPEB Plan | Level 3 | International equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.2 | 0.0 |
OPEB Plan | Level 3 | United States bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
OPEB Plan | Level 3 | International bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
OPEB Plan | Level 3 | Private equity and real estate |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 7.7 | 1.3 |
OPEB Plan | Investments measured at net asset value per share |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | $ 303.4 | $ 555.3 |

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

X
- Definition Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | wec_FairValueHierarchyandNAVAxis=wec_FairValueInputsLevel12and3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_CashAndCashEquivalentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=wec_USEquityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=wec_InternationalEquityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_USTreasuryAndGovernmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_PrivateEquityFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | wec_FairValueHierarchyandNAVAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | wec_FairValueHierarchyandNAVAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | wec_FairValueHierarchyandNAVAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | wec_FairValueHierarchyandNAVAxis=wec_FairValueMeasuredatNetAssetValuePerShareMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |