Madison Gas and Electric Company Consolidated Statements of Common Equity (USD $) In Thousands, unless otherwise specified	Total USD ($)	MGE [Member] USD ($)	Common Stock [Member]	Common Stock [Member] MGE [Member] USD ($)	Additional Paid-In Capital [Member] MGE [Member] USD ($)	Retained Earnings [Member] MGE [Member] USD ($)	Accumulated Other Comprehensive (Loss)/ Income [Member] USD ($)	Accumulated Other Comprehensive (Loss)/ Income [Member] MGE [Member] USD ($)	Noncontrolling Interest [Member] MGE [Member] USD ($)
Beginning balance, value at Dec. 31, 2011		$ 527,277		$ 17,348	$ 192,417	$ 203,114		$ 47	$ 114,351
Beginning balance, shares at Dec. 31, 2011			34,668	17,348
Increase (Decrease) in Common Equity [Roll Forward]
Net Income		65,306				40,817			24,489
Other comprehensive income/(loss)	(18)	(43)					(18)	(43)
Cash dividends paid to parent by MGE	(44,343)	(20,404)				(20,404)
Equity contribution received by noncontrolling interest		2,130							2,130
Distributions to parent from noncontrolling interest		(23,500)							(23,500)
Ending balance, value at Dec. 31, 2012		550,766		17,348	192,417	223,527		4	117,470
Ending balance, shares at Dec. 31, 2012			34,668	17,348
Increase (Decrease) in Common Equity [Roll Forward]
Net Income		76,445				49,007			27,438
Other comprehensive income/(loss)	283	188					283	188
Cash dividends paid to parent by MGE	(52,366)	(25,000)				(25,000)
Equity contribution received by noncontrolling interest		1,420							1,420
Distributions to parent from noncontrolling interest		(27,365)							(27,365)
Ending balance, value at Dec. 31, 2013		576,454		17,348	192,417	247,534		192	118,963
Ending balance, shares at Dec. 31, 2013			34,668	17,348
Increase (Decrease) in Common Equity [Roll Forward]
Net Income		81,938				55,628			26,310
Other comprehensive income/(loss)	81	(48)					81	(48)
Cash dividends paid to parent by MGE	(47,859)	(26,500)				(26,500)
Equity contribution received by noncontrolling interest		1,775							1,775
Distributions to parent from noncontrolling interest		(21,359)							(21,359)
Ending balance, value at Dec. 31, 2014		$ 612,260		$ 17,348	$ 192,417	$ 276,662		$ 144	$ 125,689
Ending balance, shares at Dec. 31, 2014			34,668	17,348