Madison Gas and Electric Company Consolidated Statements of Common Equity (Unaudited) (USD $) In Thousands, unless otherwise specified	Total USD ($)	MGE [Member] USD ($)	Common Stock [Member]	Common Stock [Member] MGE [Member] USD ($)	Additional Paid-In Capital [Member] MGE [Member] USD ($)	Retained Earnings [Member] MGE [Member] USD ($)	Accumulated Other Comprehensive (Loss)/Income [Member] USD ($)	Accumulated Other Comprehensive (Loss)/Income [Member] MGE [Member] USD ($)	Noncontrolling Interest [Member] MGE [Member] USD ($)
Beginning balance, value at Dec. 31, 2012		$ 550,766		$ 17,348	$ 192,417	$ 223,527		$ 4	$ 117,470
Beginning balance, shares at Dec. 31, 2012			34,668	17,348
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income		36,525				22,839			13,686
Other comprehensive income (loss)	140	28					140	28
Equity contribution received by noncontrolling interest		710							710
Distributions to parent from noncontrolling interest		(15,750)							(15,750)
Ending balance, value at Jun. 30, 2013		572,279		17,348	192,417	246,366		32	116,116
Ending balance, shares at Jun. 30, 2013			34,668	17,348
Beginning balance, value at Mar. 31, 2013
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income		13,965
Ending balance, value at Jun. 30, 2013		572,279		17,348	192,417
Ending balance, shares at Jun. 30, 2013			34,668	17,348
Beginning balance, value at Dec. 31, 2013		576,454		17,348	192,417	247,534		192	118,963
Beginning balance, shares at Dec. 31, 2013			34,668	17,348
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income		41,786				28,655			13,131
Other comprehensive income (loss)	(39)	(98)					(39)	(98)
Cash dividends paid to parent by MGE		(16,750)				(16,750)
Equity contribution received by noncontrolling interest		1,065							1,065
Distributions to parent from noncontrolling interest		(12,838)							(12,838)
Ending balance, value at Jun. 30, 2014		589,619		17,348	192,417	259,439		94	120,321
Ending balance, shares at Jun. 30, 2014			34,668	17,348
Beginning balance, value at Mar. 31, 2014
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income		14,143
Ending balance, value at Jun. 30, 2014		$ 589,619		$ 17,348	$ 192,417
Ending balance, shares at Jun. 30, 2014			34,668	17,348