Madison Gas and Electric Company Consolidated Statements of Common Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	MGE [Member]	Common Stock [Member]	Common Stock [Member] MGE [Member]	Additional Paid-In Capital [Member] MGE [Member]	Retained Earnings [Member]	Retained Earnings [Member] MGE [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]	Accumulated Other Comprehensive Income/(Loss) [Member] MGE [Member]	Noncontrolling Interest [Member] MGE [Member]
Beginning balance, shares at Dec. 31, 2014			34,668	17,348
Beginning balance, value before adjustments at Dec. 31, 2014		$ 612,260					$ 276,662
Cumulative effect of new accounting principle at Dec. 31, 2014	$ (142)	(142)				$ (142)	(142)
Beginning balance, value at Dec. 31, 2014		612,118		$ 17,348	$ 192,417		276,520		$ 144	$ 125,689
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income		60,240					40,428			19,812
Other comprehensive loss	(180)	(137)						$ (180)	(137)
Cash dividends paid to parent by MGE		(20,000)					(20,000)
Equity contribution received by noncontrolling interest		3,053								3,053
Distributions to parent from noncontrolling interest		(12,007)								(12,007)
Ending balance, shares at Sep. 30, 2015			34,668	17,348
Ending balance, value at Sep. 30, 2015		643,267		$ 17,348	192,417		296,948		7	136,547
Beginning balance, shares at Dec. 31, 2015			34,668	17,348
Beginning balance, value at Dec. 31, 2015		641,984		$ 17,348	192,417		291,888		23	140,308
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income		60,949					43,050			17,899
Other comprehensive loss	$ (143)	(31)						$ (143)	(31)
Cash dividends paid to parent by MGE		(40,000)					(40,000)
Equity contribution received by noncontrolling interest		1,598								1,598
Distributions to parent from noncontrolling interest		(18,113)								(18,113)
Deconsolidation of noncontrolling interest		(25,486)								(25,486)
Ending balance, shares at Sep. 30, 2016			34,668	17,348
Ending balance, value at Sep. 30, 2016		$ 620,901		$ 17,348	$ 192,417		$ 294,938		$ (8)	$ 116,206