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	$ 39,554	36,013				24,902		11,111
Capital contributions from parent		0
Distributions to parent from noncontrolling interest		(11,500)						(11,500)
Ending balance, shares at Jun. 30, 2019			34,668	17,348
Ending balance, value at Jun. 30, 2019		714,323		$ 17,348	192,417	363,493	0	141,065
Beginning balance, shares at Mar. 31, 2019			34,668	17,348
Beginning balance, value at Mar. 31, 2019		704,380		$ 17,348	192,417	355,171	0	139,444
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income	15,548	13,943				8,322		5,621
Distributions to parent from noncontrolling interest		(4,000)						(4,000)
Ending balance, shares at Jun. 30, 2019			34,668	17,348
Ending balance, value at Jun. 30, 2019		714,323		$ 17,348	192,417	363,493	0	141,065
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	44,828	40,958				29,697		11,261
Capital contributions from parent		30,000			30,000
Distributions to parent from noncontrolling interest		(8,500)						(8,500)
Ending balance, shares at Jun. 30, 2020			36,163	17,348
Ending balance, value at Jun. 30, 2020		840,047		$ 17,348	252,917	426,718	0	143,064
Beginning balance, shares at Mar. 31, 2020			34,668	17,348
Beginning balance, value at Mar. 31, 2020		795,146		$ 17,348	222,917	416,085	0	138,796
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income	$ 18,791	16,401				10,633		5,768
Capital contributions from parent		30,000			30,000
Distributions to parent from noncontrolling interest		(1,500)						(1,500)
Ending balance, shares at Jun. 30, 2020			36,163	17,348
Ending balance, value at Jun. 30, 2020		$ 840,047		$ 17,348	$ 252,917	$ 426,718	$ 0	$ 143,064