Investment in ATC (Details-1) (USD $)	9 Months Ended		0 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 MGE Transco [Member] ATC [Member]	Sep. 30, 2013 MGE Transco [Member] ATC [Member]	Dec. 31, 2013 MGE Transco [Member] ATC [Member]	Oct. 31, 2014 MGE Transco [Member] ATC [Member] Subsequent Event [Member]
Schedule Of Equity Method Investments [Line Items]
Equity earnings from investment	$ 7,306,000	$ 7,045,000	$ 7,306,000	$ 7,045,000
Dividend income from investment	5,762,000	5,498,000	5,762,000	5,498,000
Capital contributions to investment	1,830,000	1,305,000	1,420,000	1,065,000		400,000
Equity method investment			$ 67,500,000		$ 64,500,000

This item represents disclosure of the amount of dividends or other distributions received from unconsolidated subsidiaries, certain corporate joint ventures, and certain noncontrolled corporation; these investments are accounted for under the equity method of accounting. This element excludes distributions that constitute a return of investment, which are classified as investing activities.

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This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References

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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

+ References

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

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The cash outflow associated with the acquisition of or advances to an entity that is related to it but not strictly controlled (for example, an unconsolidated subsidiary, affiliate, and joint venture or equity method investment) or the acquisition of an additional interest in a subsidiary (controlled entity).

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