MGE Energy Inc Consolidated Statements of Common Equity (Unaudited) (USD $) In Thousands, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]
Beginning balance, value at Dec. 31, 2012	$ 579,429	$ 34,668	$ 316,268	$ 228,399	$ 94
Beginning balance, shares at Dec. 31, 2012		34,668
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income	22,584			22,584
Other comprehensive income (loss)	65				65
Common stock dividends declared	(9,132)			(9,132)
Ending balance, value at Mar. 31, 2013	592,946	34,668	316,268	241,851	159
Ending balance, shares at Mar. 31, 2013		34,668
Beginning balance, value at Dec. 31, 2013	617,510	34,668	316,268	266,197	377
Beginning balance, shares at Dec. 31, 2013		34,668
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income	27,717			27,717
Other comprehensive income (loss)	7				7
Common stock dividends declared	(9,420)			(9,420)
Cash in lieu of fractional shares related to stock split	(80)			(80)
Ending balance, value at Mar. 31, 2014	$ 635,734	$ 34,668	$ 316,268	$ 284,414	$ 384
Ending balance, shares at Mar. 31, 2014		34,668