MGE Energy Inc Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Other Comprehensive Income [Abstract]
Net Income	$ 11,232	$ 28,354	$ 13,479	$ 18,278	$ 15,186	$ 23,329	$ 14,087	$ 27,717	$ 71,343	$ 80,319	$ 74,905
Other comprehensive income/(loss), net of tax:
Unrealized (loss) gain on available for sale securities, net of tax									(101)	81	283
Comprehensive Income									$ 71,242	$ 80,400	$ 75,188