Consolidated Statements of Capitalization (Parenthetical) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Debentures (unsecured), 6.00% due 2014 [Member]
Debt instrument stated interest rate (percentage)	6.00%	6.00%
Debentures (unsecured), 5.20% due 2015 [Member]
Debt instrument stated interest rate (percentage)	5.20%	5.20%
Debentures (unsecured), 6.25% due 2015 [Member]
Debt instrument stated interest rate (percentage)	6.25%	6.25%
Debentures (unsecured), 1.70% due 2018 [Member]
Debt instrument stated interest rate (percentage)	1.70%	1.70%
Debentures (unsecured), 4.25% due 2019 [Member]
Debt instrument stated interest rate (percentage)	4.25%	4.25%
Debentures (unsecured) 2.95% due 2021 [Member]
Debt instrument stated interest rate (percentage)	2.95%	2.95%
Debentures (unsecured), 6-1/2% due 2028 [Member]
Debt instrument stated interest rate (percentage)	6.50%	6.50%
Debentures (unsecured), 5.625% due 2033 [Member]
Debt instrument stated interest rate (percentage)	5.625%	5.625%
Debentures (unsecured), 5.90% due 2035 [Member]
Debt instrument stated interest rate (percentage)	5.90%	5.90%
Debentures (unsecured), 5.70% due 2036 [Member]
Debt instrument stated interest rate (percentage)	5.70%	5.70%
Debentures (unsecured), 3.65% due 2042 [Member]
Debt instrument stated interest rate (percentage)	3.65%	3.65%
Debentures (unsecured), 4.25% due 2044 [Member]
Debt instrument stated interest rate (percentage)	4.25%	4.25%
Debentures (unsecured), 6-7/8% due 2095 [Member]
Debt instrument stated interest rate (percentage)	6.875%	6.875%
Notes (secured, nonrecourse), 4.81% effective rate due 2030 [Member]
Debt instrument stated interest rate (percentage)	4.81%	4.81%
Notes (secured, nonrecourse), 4.91% due 2014-2030 [Member] [Member]
Debt instrument stated interest rate (percentage)	4.91%	4.91%
Notes (secured, nonrecourse), 5.209% due 2014-2030 [Member] [Member]
Debt instrument stated interest rate (percentage)	5.209%	5.209%
Notes (secured, nonrecourse), 4.673% due 2014-2031 [Member] [Member]
Debt instrument stated interest rate (percentage)	4.673%	4.673%
Notes (secured, nonrecourse), 6.00% due 2014-2033 [Member] [Member]
Debt instrument stated interest rate (percentage)	6.00%	6.00%
Notes (secured, nonrecourse), 6.09% due 2030-2040 [Member]
Debt instrument stated interest rate (percentage)	6.09%	6.09%
Notes (secured, nonrecourse), 5.848% due 2031-2041 [Member]
Debt instrument stated interest rate (percentage)	5.848%	5.848%
Notes (secured, nonrecourse) 6.00% due 2021 [Member]
Debt instrument stated interest rate (percentage)	6.00%	6.00%
Notes (unsecured), 6.94% due 2028 [Member]
Debt instrument stated interest rate (percentage)	6.94%	6.94%
Notes (unsecured), 6.20% due 2033 [Member]
Debt instrument stated interest rate (percentage)	6.20%	6.20%
Junior Notes (unsecured), 6.25% due 2067 [Member]
Debt instrument stated interest rate (percentage)	6.25%	6.25%
Wisconsin Energy Corporation [Member]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	15,000,000	15,000,000
Preferred stock, shares outstanding	0	0
Six Per Cent. Preferred Stock [Member]
Preferred stock, shares authorized	45,000
Preferred stock, shares outstanding	44,498
Six Per Cent. Preferred Stock [Member] \| Wisconsin Electric [Member]
Preferred stock, par value	$ 100	$ 100
Preferred stock, shares authorized		45,000
Preferred stock, shares outstanding		44,498
Preferred stock dividend rate, percentage	6.00%	6.00%
Serial preferred stock, 3.60% Series Redeemable [Member]
Preferred stock, shares outstanding	260,000
Serial preferred stock, 3.60% Series Redeemable [Member] \| Wisconsin Electric [Member]
Preferred stock, par value	$ 100	$ 100
Preferred stock, shares outstanding		260,000
Preferred stock dividend rate, percentage	3.60%	3.60%

Contractual interest rate for funds borrowed, under the debt agreement.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: 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

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+ References

No definition available.

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+ 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 210.5-02.28)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29

-Article 5

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+ References

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Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

+ References

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