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		60,856				40,309			20,547
Other comprehensive income (loss)	176	77					176	77
Equity contribution received by noncontrolling interest		1,065							1,065
Distributions to parent from noncontrolling interest		(21,148)							(21,148)
Ending balance, value at Sep. 30, 2013		591,616		17,348	192,417	263,836		81	117,934
Ending balance, shares at Sep. 30, 2013			34,668	17,348
Beginning balance, value at Jun. 30, 2013
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income		24,331
Ending balance, value at Sep. 30, 2013		591,616		17,348	192,417
Ending balance, shares at Sep. 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		65,255				45,471			19,784
Other comprehensive income (loss)	56	(54)					56	(54)
Cash dividends paid to parent by MGE		(26,500)				(26,500)
Equity contribution received by noncontrolling interest		1,420							1,420
Distributions to parent from noncontrolling interest		(17,778)							(17,778)
Ending balance, value at Sep. 30, 2014		598,797		17,348	192,417	266,505		138	122,389
Ending balance, shares at Sep. 30, 2014			34,668	17,348
Beginning balance, value at Jun. 30, 2014
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income		23,469
Ending balance, value at Sep. 30, 2014		$ 598,797		$ 17,348	$ 192,417
Ending balance, shares at Sep. 30, 2014			34,668	17,348