XML 81 R65.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Summary of Significant Accounting Policies Materials, Supplies, and Inventories (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 USD ($) $ / Dekatherm | Dec. 31, 2016 USD ($) $ / Dekatherm
Inventory |  |
Natural gas in storage | $ 209.0 | $ 223.1
Materials and supplies | 211.2 | 206.5
Fossil fuel | 118.8 | 158.0
Total | $ 539.0 | $ 587.6
Percentage of LIFO inventory | 15.00% | 18.00%
PGL and NSG |  |
Inventory |  |
Excess of replacement or current costs over stated LIFO value | $ 152.1 | $ 92.9
Natural gas price benchmark | $ / Dekatherm | 4.68 | 3.63

X
- Definition Carrying amount as of the balance sheet date of merchandise, goods, commodities, or supplies relating to a source of usable power held for future sale or future use in manufacturing or production process. + 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 210.5-02.6(a)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_EnergyRelatedInventory
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Carrying amount as of the balance sheet date of natural gas in storage, which is a mixture of gases (liquefied or otherwise), used for fuel and manufacturing purposes, which is ready for sale. + 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 210.5-02.6(a)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_EnergyRelatedInventoryNaturalGasInStorage
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of fossil fuel included in inventory classified as other. + 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 210.5-02.6(a)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_EnergyRelatedInventoryOtherFossilFuel
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The excess of replacement or current cost over the stated LIFO (last in first out) inventory value when the LIFO inventory method is utilized. + 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 210.5-02.6(c)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_ExcessOfReplacementOrCurrentCostsOverStatedLIFOValue
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_InventoryLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Aggregated amount of unprocessed materials to be used in manufacturing or production process and supplies that will be consumed. This amount is net of valuation reserves and adjustments. + 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(6)(a)(4)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 330 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 5.BB) -URI http://asc.fasb.org/extlink&oid=27011343&loc=d3e100047-122729 Reference 3: 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(6)(a)(5)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_InventoryRawMaterialsAndSuppliesNetOfReserves
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The percentage of LIFO (last in first out) inventory to total inventory as of the balance sheet date if other than 100 percent. + References No definition available. + Details
Name: | us-gaap_PercentageOfLIFOInventory
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents the Chicago city-gate natural gas price used in calculating replacement amounts. + References No definition available. + Details
Name: | wec_NaturalGasPriceBenchmark
Namespace Prefix: | wec_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

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