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		33,287				21,083			12,204
Other comprehensive income (loss)	$ (154)	(39)					$ (154)	(39)
Cash dividends paid to parent by MGE		(25,000)				(25,000)
Equity contribution received by noncontrolling interest		710							710
Distributions to parent from noncontrolling interest		(10,552)							(10,552)
Ending balance, shares at Jun. 30, 2016			34,668	17,348
Ending balance, value at Jun. 30, 2016		640,390		$ 17,348	192,417	287,971		(16)	142,670
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		32,333				21,548			10,785
Other comprehensive income (loss)	$ 129	(31)					$ 129	(31)
Cash dividends paid to parent by MGE		(25,000)				(25,000)
Distributions to parent from noncontrolling interest		(10,000)							(10,000)
Ending balance, shares at Jun. 30, 2017			34,668	17,348
Ending balance, value at Jun. 30, 2017		$ 600,051		$ 17,348	$ 192,417	$ 273,848		$ (12)	$ 116,450