Investment in ATC (Details-1) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Schedule Of Equity Method Investments [Line Items]
Equity earnings from investment	$ 2,233	$ 1,881
Dividend income from investment	865	1,420
Contributions to investments	671	280
MGE Transco [Member] \| ATC [Member]
Schedule Of Equity Method Investments [Line Items]
Equity earnings from investment	2,233	1,881
Dividend income from investment	865	1,420
Contributions to investments	533	178
Equity method investment	71,400		$ 69,500
MGE [Member]
Schedule Of Equity Method Investments [Line Items]
Equity earnings from investment	2,233	1,881
Dividend income from investment	865	1,420
Contributions to investments	$ 533	$ 178
Minority Interest [Line Items]
MGE's ownership interest in MGE Transco	51.00%
MGE Energy [Member]
Minority Interest [Line Items]
MGE Energy's ownership interest in MGE Transco	49.00%

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+ References

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