Schedule I - Condensed Parent Company Finanical Statements (Details-Cash Flow Statement) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Flows Provided by (Used for) Operating Activities	$ 128,762	$ 140,267	$ 146,004
Investing Activities:
Other investing	(1,297)	(1,205)	(496)
Cash Provided by (Used for) Investing Activities	(96,158)	(121,922)	(101,353)
Financing Activities:
Cash dividends paid on common stock	(38,429)	(37,107)	(35,951)
Change in short-term debt	7,000	0	0
Other financing	(130)	(770)	(844)
Cash Provided by (Used for) Financing Activities	(35,662)	4,111	(39,463)
Change in Cash and Cash Equivalents:	(3,058)	22,456	5,188
Cash and cash equivalents at beginning of period	68,813	46,357	41,169
Cash and cash equivalents at end of period	65,755	68,813	46,357
MGE Energy [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Flows Provided by (Used for) Operating Activities	48,165	53,952	49,819
Investing Activities:
Other investing	(2,422)	(2,425)	(1,558)
Cash Provided by (Used for) Investing Activities	(2,422)	(2,425)	(1,558)
Financing Activities:
Cash dividends paid on common stock	(38,429)	(37,107)	(35,951)
Other financing	(89)	(97)	(49)
Cash Provided by (Used for) Financing Activities	(38,518)	(37,204)	(36,000)
Change in Cash and Cash Equivalents:	7,225	14,323	12,261
Cash and cash equivalents at beginning of period	51,204	36,881	24,620
Cash and cash equivalents at end of period	$ 58,429	$ 51,204	$ 36,881