Condensed Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) $ in Millions	9 Months Ended
Sep. 30, 2015 USD ($)
Derivatives accounted for as cash flow hedges
Gains on settlement, tax	$ 7.6

Amount of tax expense (benefit), before reclassification adjustments, related to increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

No definition available.

Name:	wec_OtherComprehensiveIncomeRealizedGainLossOnDerivativesArisingDuringPeriodTax
Namespace Prefix:	wec_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration