Noncontrolling Interest (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
MGE [Member]
Noncontrolling Interest [Line Items]
Noncontrolling interest on balance sheet		$ 140,308	$ 125,689
Net income attributable to noncontrolling interest, net of tax		26,097	26,310	$ 27,438
MGE Transco [Member]
Noncontrolling Interest [Line Items]
Noncontrolling interest on balance sheet	[1]	23,592	22,397
Net income attributable to noncontrolling interest, net of tax	[1]	$ 2,172	2,484	2,408
MGE Power [Member]
Noncontrolling Interest [Line Items]
Ownership percentage by parent		100.00%
MGE Power West Campus [Member]
Noncontrolling Interest [Line Items]
Ownership percentage by parent		100.00%
Noncontrolling interest on balance sheet	[2]	$ 37,603	30,755
Net income attributable to noncontrolling interest, net of tax	[2]	$ 7,348	7,666	7,657
MGE Power Elm Road [Member]
Noncontrolling Interest [Line Items]
Ownership percentage by parent		100.00%
Noncontrolling interest on balance sheet	[2]	$ 79,113	72,537
Net income attributable to noncontrolling interest, net of tax	[2]	$ 16,577	$ 16,160	$ 17,373

[1] At December 31, 2015 , MGE is the majority owner, and MGE Energy is the minority owner, of MGE Transco. MGE Energy's proportionat e share of the equity and net income of MGE Transco is classified within the MGE consolidated financial statements as noncontrolling interest . In mid-2016, MGE is no longer expected to be the majority owner of MGE Transco. The change will have no effect on MGE Energy' s consolidated financial statements; however, MGE Energy ' s proportionate share of the equity and net income of MGE Transco will be deconsolidated from MGE’s financial statements. No gain or loss is expected to be recognized on the date MGE ceases to have a controlling financial interest .

[2] MGE Power Elm Road and MGE Power West Campus are not su bsidiaries of MGE; however, they have been consolidated in the consolidated financial statements of MGE (see Footnote 2). MGE Power Elm Road and MGE Power West Campus are 100 % owned by MGE Power , and MGE Power is 100 % owned by MGE Energy. MGE Energy's proportionate share of the equity and net income (through its wholly owned subsidiary MGE Power) of MGE Power Elm Road and MGE Power West Campus is classified within the MGE consolidated financial statements as noncontrolling interest.