Condensed Parent Company Financial Statements (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Parent Company long-term debt outstanding
Next year	$ 399.5
Year 2	27.4
Year 3	29.5
Year 4	281.1
Year 5	282.7
Thereafter	3,532.2
Total	4,552.4us-gaap_DebtInstrumentFaceAmount
Wisconsin Energy Corporation [Member]
Parent Company long-term debt outstanding
Next year	0
Year 2	0
Year 3	0
Year 4	0
Year 5	0
Thereafter	700.0
Total	700.0
Junior Notes (unsecured), 6.25% due 2067 [Member]
Parent Company long-term debt outstanding
Unsecured Long-term Debt, Noncurrent	$ 500.0	$ 500.0
Interest Rate effective May 2017 for Junior Notes	the three-month LIBOR Rate plus 211.25 basis points and will reset quarterly

Face (par) amount of debt instrument at time of issuance.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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