Schedule I - Condensed Parent Company Finanical Statements (Details-Cash Flow Statement) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Flows Provided by (Used for) Operating Activities	$ 140,267	$ 146,004	$ 130,772
Investing Activities:
Other investing	(1,205)	(496)	1,985
Cash Provided by (Used for) Investing Activities	(121,922)	(101,353)	(66,351)
Financing Activities:
Cash dividends paid on common stock	(37,107)	(35,951)	(35,026)
Change in short-term debt	0	0	(22,500)
Other financing	(770)	(844)	(336)
Cash Provided by (Used for) Financing Activities	4,111	(39,463)	(30,362)
Change in Cash and Cash Equivalents:	22,456	5,188	34,059
Cash and cash equivalents at beginning of period	46,357	41,169	7,110
Cash and cash equivalents at end of period	68,813	46,357	41,169
MGE Energy [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Flows Provided by (Used for) Operating Activities	53,952	49,819	50,696
Investing Activities:
Return of investment - affiliates	0	0	30,000
Other investing	(2,425)	(1,558)	(3,022)
Cash Provided by (Used for) Investing Activities	(2,425)	(1,558)	26,978
Financing Activities:
Cash dividends paid on common stock	(37,107)	(35,951)	(35,026)
Change in short-term debt	0	0	(19,000)
Other financing	(97)	(49)	0
Cash Provided by (Used for) Financing Activities	(37,204)	(36,000)	(54,026)
Change in Cash and Cash Equivalents:	14,323	12,261	23,648
Cash and cash equivalents at beginning of period	36,881	24,620	972
Cash and cash equivalents at end of period	$ 51,204	$ 36,881	$ 24,620