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] MGE [Member]	Noncontrolling Interest [Member] MGE [Member]
Beginning balance, shares at Dec. 31, 2018			34,668	17,348
Beginning balance, value at Dec. 31, 2018		$ 689,810		$ 17,348	$ 192,417	$ 338,591	$ 0	$ 141,454
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income	$ 24,007	22,070				16,580		5,490
Distributions to parent from noncontrolling interest		(7,500)						(7,500)
Ending balance, shares at Mar. 31, 2019			34,668	17,348
Ending balance, value at Mar. 31, 2019		704,380		$ 17,348	192,417	355,171	0	139,444
Beginning balance, shares at Dec. 31, 2019			34,668	17,348
Beginning balance, value at Dec. 31, 2019		777,589		$ 17,348	222,917	397,021	0	140,303
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income	$ 26,037	24,557				19,064		5,493
Distributions to parent from noncontrolling interest		(7,000)						(7,000)
Ending balance, shares at Mar. 31, 2020			34,668	17,348
Ending balance, value at Mar. 31, 2020		$ 795,146		$ 17,348	$ 222,917	$ 416,085	$ 0	$ 138,796