Consolidated Statements of Common Equity (Unaudited) (Parentheticals) (USD $) In Thousands, except Per Share data	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
MGE Energy [Member]
Consolidated Statements of Common Equity and Comprehensive Income
Unrealized gain (loss) on available-for-sale securities, taxes	$ (50)	$ 6	$ 4	$ (48)
Reclassification of realized gain on available-for-sale securities, taxes	0	0	(10)	0
Dividends per share of common stock	$ 0.383	$ 0.375	$ 1.133	$ 1.112
MGE [Member]
Consolidated Statements of Common Equity and Comprehensive Income
Unrealized gain (loss) on available-for-sale securities, taxes	(35)	2	(14)	(32)
Reclassification of realized gain on available-for-sale securities, taxes	$ 0	$ 0	$ (10)	$ 0

Tax effect on the reclassification adjustment for gains or losses realized upon the sale of securities during the period.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 130

-Paragraph 25

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e640-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 38

-Subparagraph c(3)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration