Madison Gas and Electric Company Consolidated Statements of Common Equity (Unaudited) (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 ($)	Retained Earnings [Member] USD ($)	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, 2013		$ 576,454		$ 17,348	$ 192,417		$ 247,534		$ 192	$ 118,963
Beginning balance, shares at Dec. 31, 2013			34,668	17,348
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income		27,643					21,133			6,510
Other comprehensive income (loss)	7	18						7	18
Cash dividends paid to parent by MGE		(7,000)					(7,000)
Equity contribution received by noncontrolling interest		533								533
Distributions to parent from noncontrolling interest		(6,909)								(6,909)
Ending balance, value at Mar. 31, 2014		590,739		17,348	192,417		261,667		210	119,097
Ending balance, shares at Mar. 31, 2014			34,668	17,348
Beginning balance, value - Adjusted at Dec. 31, 2014		612,118					276,520
Beginning balance, value at Dec. 31, 2014		612,260		17,348	192,417		276,662		144	125,689
Beginning balance, shares at Dec. 31, 2014			34,668	17,348
Cumulative effect of new accounting principle (See Footnote 4) at Dec. 31, 2014	(142)	(142)				(142)	(142)
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income		18,311					11,758			6,553
Other comprehensive income (loss)	(85)	(82)						(85)	(82)
Equity contribution received by noncontrolling interest		2,678								2,678
Distributions to parent from noncontrolling interest		(6,818)								(6,818)
Ending balance, value at Mar. 31, 2015		$ 626,207		$ 17,348	$ 192,417		$ 288,278		$ 62	$ 128,102
Ending balance, shares at Mar. 31, 2015			34,668	17,348