Schedule I - Condensed Parent Company Finanical Statements (Details-Comprehensive Income Statement) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Expenses:
Other operations and maintenance									$ 164,478	$ 161,703	$ 171,248
Total Operating Expenses	$ 108,795	$ 94,618	$ 98,077	$ 138,283	$ 116,141	$ 95,015	$ 104,324	$ 166,274	439,773	481,754	462,900
Operating Income (Loss)	22,178	46,177	24,049	31,851	29,566	40,120	24,441	43,971	124,255	138,098	127,987
Equity in earnings of investments									7,728	9,150	9,434
Income before income taxes									112,706	128,504	119,764
Income tax provision	(7,417)	(15,351)	(8,008)	(10,587)	(8,600)	(14,286)	(9,034)	(16,265)	(41,363)	(48,185)	(44,859)
Net Income	$ 11,232	$ 28,354	$ 13,479	$ 18,278	$ 15,186	$ 23,329	$ 14,087	$ 27,717	71,343	80,319	74,905
Other comprehensive income/(loss), net of tax:
Unrealized (loss) gain on available for sale securities, net of tax									(101)	81	283
Comprehensive Income									71,242	80,400	75,188
MGE Energy [Member]
Operating Expenses:
Other operations and maintenance									690	689	613
Total Operating Expenses									690	689	613
Operating Income (Loss)									(690)	(689)	(613)
Equity in earnings of investments									71,306	81,811	76,362
Other income/(loss), net									526	(1,879)	(1,863)
Other interest									136	93	55
Income before income taxes									71,278	79,336	73,941
Income tax provision									65	983	964
Net Income									71,343	80,319	74,905
Other comprehensive income/(loss), net of tax:
Unrealized (loss) gain on available for sale securities, net of tax									(101)	81	283
Comprehensive Income									$ 71,242	$ 80,400	$ 75,188