XML 61 R49.htm IDEA: XBRL DOCUMENT
v3.7.0.1

LONG TERM DEBT (Details) $ in Millions | 6 Months Ended
--- | ---
Jun. 30, 2017 USD ($)
WEC Energy Group | 2007 Junior Notes (unsecured), due 2067 |
Debt Instrument [Line Items] |
Interest rate percentage in excess of LIBOR | 2.1125%
Unsecured Long-term Debt, Noncurrent | $ 500.0
MERC |
Debt Instrument [Line Items] |
Proceeds from Issuance of Debt | 120.0
MERC | MERC Senior Notes 3.11% due July 15, 2027 |
Debt Instrument [Line Items] |
Proceeds from Issuance of Debt | $ 40.0
Interest rate on long-term debt | 3.11%
MERC | MERC Senior Notes 3.41% due July 15, 2032 |
Debt Instrument [Line Items] |
Proceeds from Issuance of Debt | $ 40.0
Interest rate on long-term debt | 3.41%
MERC | MERC Senior Notes 4.01% due July 15, 2047 |
Debt Instrument [Line Items] |
Proceeds from Issuance of Debt | $ 40.0
Interest rate on long-term debt | 4.01%
MGU |
Debt Instrument [Line Items] |
Proceeds from Issuance of Debt | $ 90.0
MGU | MGU Senior Notes 3.11% due July 15, 2027 |
Debt Instrument [Line Items] |
Proceeds from Issuance of Debt | $ 30.0
Interest rate on long-term debt | 3.11%
MGU | MGU Senior Notes 3.41% due July 15, 2032 |
Debt Instrument [Line Items] |
Proceeds from Issuance of Debt | $ 30.0
Interest rate on long-term debt | 3.41%
MGU | MGU Senior Notes 4.01% due July 15, 2047 |
Debt Instrument [Line Items] |
Proceeds from Issuance of Debt | $ 30.0
Interest rate on long-term debt | 4.01%
Integrys | MERC |
Debt Instrument [Line Items] |
Repayment of long-term debt from parent | $ 78.0
Integrys | MGU |
Debt Instrument [Line Items] |
Repayment of long-term debt from parent | $ 71.0

X
- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
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_DebtInstrumentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt. + References No definition available. + Details
Name: | us-gaap_ProceedsFromIssuanceOfDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Carrying value as of the balance sheet date of uncollateralized debt obligation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_UnsecuredLongTermDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Interest rate percentage in excess of LIBOR + References No definition available. + Details
Name: | wec_InterestratepercentageinexcessofLIBOR
Namespace Prefix: | wec_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Repayment of long-term debt from parent + References No definition available. + Details
Name: | wec_Repaymentoflongtermdebtfromparent
Namespace Prefix: | wec_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=us-gaap_ParentCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=wec_JuniorNotesUnsecured625Due2067Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=wec_MERCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=wec_MERCSeniorNotes3.11dueJuly152027Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=wec_MERCSeniorNotes3.41dueJuly152032Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=wec_MERCSeniorNotes4.01dueJuly152047Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=wec_MGUMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=wec_MGUSeniorNotes3.11dueJuly152027Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=wec_MGUSeniorNotes3.41dueJuly152032Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=wec_MGUSeniorNotes4.01dueJuly152047Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=wec_IntegrysMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |