Condensed Parent Company Financial Statements (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Parent Company Income Statement
Other Income, Net	$ 13.4us-gaap_OtherNonoperatingIncomeExpense	$ 18.8us-gaap_OtherNonoperatingIncomeExpense	$ 34.8us-gaap_OtherNonoperatingIncomeExpense
Interest Expense, net	241.5us-gaap_InterestExpense	252.1us-gaap_InterestExpense	248.2us-gaap_InterestExpense
Income (Loss) from Continuing Operations Before Income Taxes	950.0	915.3	852.6
Income Tax Benefit	(361.7)us-gaap_IncomeTaxExpenseBenefit	(337.9)us-gaap_IncomeTaxExpenseBenefit	(306.3)us-gaap_IncomeTaxExpenseBenefit
Net Income	588.3us-gaap_NetIncomeLoss	577.4us-gaap_NetIncomeLoss	546.3us-gaap_NetIncomeLoss
Subsidiaries [Member]
Condensed Parent Company Income Statement
Income from Continuing Operations	635.0	607.8	577.6
Wisconsin Energy Corporation [Member]
Condensed Parent Company Income Statement
Other Income, Net	2.8	3.1	3.2
Corporate Expense	26.8	5.5	4.8
Interest Expense, net	53.1	54.4	55.7
Income (Loss) from Continuing Operations Before Income Taxes	(77.1)	(56.8)	(57.3)
Income Tax Benefit	30.4	26.4	26.0
Income from Continuing Operations	(46.7)	(30.4)	(31.3)
Net Income	$ 588.3	$ 577.4	$ 546.3

Amount of income (loss) from continuing operations attributable to the parent. Also defined as revenue less expenses and taxes from ongoing operations before extraordinary items but after deduction of those portions of income or loss from continuing operations that are allocable to noncontrolling interests.

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Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the cost of borrowed funds accounted for as interest expense.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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The net amount of other income and expense amounts, the components of which are not separately disclosed on the income statement, resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating income (expense) recognized for the period. Such amounts may include: (a) dividends, (b) interest on securities, (c) net gains or losses on securities, (d) unusual costs, (e) gains or losses on foreign exchange transactions, and (f) miscellaneous other income and expense items.

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Corporate Expense.

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