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] 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, 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		17,197				10,945			6,252
Other comprehensive income (loss)	$ (164)	(30)					$ (164)	(30)
Cash dividends paid to parent by MGE		(10,000)				(10,000)
Equity contribution received by noncontrolling interest		533							533
Distributions to parent from noncontrolling interest		(6,500)							(6,500)
Ending balance, shares at Mar. 31, 2016			34,668	17,348
Ending balance, value at Mar. 31, 2016		643,184		$ 17,348	192,417	292,833		(7)	140,593
Beginning balance, shares at Dec. 31, 2016			34,668	17,348
Beginning balance, value at Dec. 31, 2016		602,749		$ 17,348	192,417	277,300		19	115,665
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income		18,183				12,794			5,389
Other comprehensive income (loss)	$ 97	(6)					$ 97	(6)
Cash dividends paid to parent by MGE		(15,000)				(15,000)
Distributions to parent from noncontrolling interest		(5,500)							(5,500)
Ending balance, shares at Mar. 31, 2017			34,668	17,348
Ending balance, value at Mar. 31, 2017		$ 600,426		$ 17,348	$ 192,417	$ 275,094		$ 13	$ 115,554