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, 2023			36,163	17,348
Beginning balance, value at Dec. 31, 2023		$ 1,053,256		$ 17,348	$ 252,917	$ 633,460	$ 0	$ 149,531
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	$ 98,547	93,064				75,924		17,140
Cash dividends paid to parent by MGE		(31,000)				(31,000)
Distributions to parent from noncontrolling interest		(16,000)						(16,000)
Ending balance, shares at Sep. 30, 2024			36,205	17,348
Ending balance, value at Sep. 30, 2024		1,099,320		$ 17,348	252,917	678,384	0	150,671
Beginning balance, shares at Jun. 30, 2024			36,176	17,348
Beginning balance, value at Jun. 30, 2024		1,073,210		$ 17,348	252,917	652,051	0	150,894
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	40,939	39,110				33,333		5,777
Cash dividends paid to parent by MGE		(7,000)				(7,000)
Distributions to parent from noncontrolling interest		(6,000)						(6,000)
Ending balance, shares at Sep. 30, 2024			36,205	17,348
Ending balance, value at Sep. 30, 2024		1,099,320		$ 17,348	252,917	678,384	0	150,671
Beginning balance, shares at Dec. 31, 2024			36,490	17,348
Beginning balance, value at Dec. 31, 2024		1,139,805		$ 17,348	283,667	688,404	0	150,386
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	112,587	104,037				87,056		16,981
Cash dividends paid to parent by MGE		(37,500)				(37,500)
Capital contributions from parent		2,000				2,000
Distributions to parent from noncontrolling interest		(11,500)						(11,500)
Ending balance, shares at Sep. 30, 2025			36,542	17,348
Ending balance, value at Sep. 30, 2025		1,196,842		$ 17,348	283,667	739,960	0	155,867
Beginning balance, shares at Jun. 30, 2025			36,542	17,348
Beginning balance, value at Jun. 30, 2025		1,172,583		$ 17,348	283,667	717,869	0	153,699
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	$ 44,497	39,759				34,091		5,668
Cash dividends paid to parent by MGE		(14,000)				(14,000)
Capital contributions from parent		2,000				2,000
Distributions to parent from noncontrolling interest		(3,500)						(3,500)
Ending balance, shares at Sep. 30, 2025			36,542	17,348
Ending balance, value at Sep. 30, 2025		$ 1,196,842		$ 17,348	$ 283,667	$ 739,960	$ 0	$ 155,867