Madison Gas and Electric Company Consolidated Statements of Equity - USD ($) shares in Thousands	Total	MGE [Member]	Common Stock [Member]	Common Stock [Member] MGE [Member]	Additional Paid-In Capital [Member] MGE [Member]	Retained Earnings [Member]	Retained Earnings [Member] MGE [Member]	Accumulated Other Comprehensive (Loss)/ Income [Member]	Accumulated Other Comprehensive (Loss)/ Income [Member] MGE [Member]	Noncontrolling Interest [Member] MGE [Member]
Beginning balance, shares at Dec. 31, 2016			34,668	17,348
Beginning balance, value at Dec. 31, 2016		$ 602,749,000		$ 17,348,000	$ 192,417,000		$ 277,300,000		$ 19,000	$ 115,665,000
Increase (Decrease) in Equity [Roll Forward]
Net Income	$ 97,606,000	93,072,000					49,835,000			43,237,000
Other comprehensive income (loss)	175,000	(47,000)						$ 175,000	(47,000)
Cash dividends paid to parent by MGE		(45,000,000)					(45,000,000)
Capital contributions from parent		0
Distributions to parent from noncontrolling interest		(18,000,000)								(18,000,000)
Ending balance, shares at Dec. 31, 2017			34,668	17,348
Ending balance, value at Dec. 31, 2017		632,774,000		$ 17,348,000	192,417,000		282,135,000		(28,000)	140,902,000
Increase (Decrease) in Equity [Roll Forward]
Cumulative effect of new accounting principle	0	0				$ 377,000	(28,000)	(377,000)	28,000
Beginning balance, value - Adjusted at Dec. 31, 2017	778,187,000	632,774,000				$ 427,251,000	282,107,000	$ 0	0
Increase (Decrease) in Equity [Roll Forward]
Net Income	84,219,000	79,036,000					56,484,000			22,552,000
Cash dividends paid to parent by MGE		0
Capital contributions from parent		0
Distributions to parent from noncontrolling interest		(22,000,000)								(22,000,000)
Ending balance, shares at Dec. 31, 2018			34,668	17,348
Ending balance, value at Dec. 31, 2018		689,810,000		$ 17,348,000	192,417,000		338,591,000		0	141,454,000
Increase (Decrease) in Equity [Roll Forward]
Net Income	$ 86,874,000	80,779,000					58,430,000			22,349,000
Cash dividends paid to parent by MGE		0
Capital contributions from parent		30,500,000			30,500,000
Distributions to parent from noncontrolling interest		(23,500,000)								(23,500,000)
Ending balance, shares at Dec. 31, 2019			34,668	17,348
Ending balance, value at Dec. 31, 2019		$ 777,589,000		$ 17,348,000	$ 222,917,000		$ 397,021,000		$ 0	$ 140,303,000