Madison Gas and Electric Company Consolidated Statements of Equity - 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]	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, 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 Equity [Roll Forward]
Net Income		74,592						51,234			23,358
Other comprehensive income (loss)	$ (155)	(4)							$ (155)	(4)
Cash dividends paid to parent by MGE		(50,000)	[1]					(50,000)
Dividend in kind to parent		(15,822)						(15,822)
Equity contribution received by noncontrolling interest		1,598									1,598
Distributions to parent from noncontrolling interest		(24,113)									(24,113)
Deconsolidation of noncontrolling interest		(25,486)									(25,486)
Ending balance, shares at Dec. 31, 2016				34,668	17,348
Ending balance, value at Dec. 31, 2016		602,749			$ 17,348	192,417		277,300		19	115,665
Increase (Decrease) in Equity [Roll Forward]
Net Income		93,072						49,835			43,237
Other comprehensive income (loss)	175	(47)							175	(47)
Cash dividends paid to parent by MGE		(45,000)						(45,000)
Dividend in kind to parent		0
Distributions to parent from noncontrolling interest		(18,000)									(18,000)
Ending balance, shares at Dec. 31, 2017				34,668	17,348
Ending balance, value at Dec. 31, 2017		632,774			$ 17,348	192,417		282,135		(28)	140,902
Increase (Decrease) in Equity [Roll Forward]
Cumulative effect of new accounting principle	0	0					$ 377	(28)	(377)	28
Beginning balance, value - Adjusted at Dec. 31, 2017	$ 778,187	632,774					$ 427,251	282,107	$ 0	0
Increase (Decrease) in Equity [Roll Forward]
Net Income		79,036						56,484			22,552
Cash dividends paid to parent by MGE		0
Dividend in kind to parent		0
Distributions to parent from noncontrolling interest		(22,000)									(22,000)
Ending balance, shares at Dec. 31, 2018				34,668	17,348
Ending balance, value at Dec. 31, 2018		$ 689,810			$ 17,348	$ 192,417		$ 338,591		$ 0	$ 141,454

[1] Excludes $15.8 million dividend in kind to MGE Energy from MGE in 2016 .