Schedule I - Condensed Parent Company Finanical Statements (Details-Cash Flow Statement) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Flows Provided by (Used for) Operating Activities	$ 141,185	$ 128,762	$ 140,267
Investing Activities:
Other investing	(230)	(1,297)	(1,205)
Cash Provided by (Used for) Investing Activities	(73,313)	(96,158)	(121,922)
Financing Activities:
Cash dividends paid on common stock	(40,043)	(38,429)	(37,107)
Change in short-term debt	(7,000)	7,000	0
Other financing	(1,018)	(130)	(770)
Cash Provided by (Used for) Financing Activities	(52,243)	(35,662)	4,111
Change in cash and cash equivalents:	15,629	(3,058)	22,456
Cash and cash equivalents at beginning of period	65,755	68,813	46,357
Cash and cash equivalents at end of period	81,384	65,755	68,813
MGE Energy [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Flows Provided by (Used for) Operating Activities	37,085	48,165	53,952
Investing Activities:
Other investing	(3,690)	(2,422)	(2,425)
Cash Provided by (Used for) Investing Activities	(3,690)	(2,422)	(2,425)
Financing Activities:
Cash dividends paid on common stock	(40,043)	(38,429)	(37,107)
Other financing	0	(89)	(97)
Cash Provided by (Used for) Financing Activities	(40,043)	(38,518)	(37,204)
Change in cash and cash equivalents:	(6,648)	7,225	14,323
Cash and cash equivalents at beginning of period	58,429	51,204	36,881
Cash and cash equivalents at end of period	$ 51,781	$ 58,429	$ 51,204