MGE Energy Inc Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Other Comprehensive Income [Abstract]
Net Income	$ 15,186	$ 23,329	$ 14,087	$ 27,717	$ 14,077	$ 24,353	$ 13,891	$ 22,584	$ 80,319	$ 74,905	$ 64,446
Other comprehensive income/(loss), net of tax:
Unrealized gain (loss) on available for sale securities, net of tax									81	283	(18)
Comprehensive Income									$ 80,400	$ 75,188	$ 64,428