Variable Interest Entities (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2015 USD ($) MW	Dec. 31, 2014 USD ($) MW
Significant Balance Sheet Accounts Related to Interests in Variable Interest Entities
Property, plant, and equipment, net		$ 1,217,094	$ 1,189,077
Construction work in progress		26,351	19,029
Accrued interest and taxes		$ 5,067	$ 5,086
Other Variable Interest Entities
Other variable interest entities, purchase power agreement, plant capacity (in MW) | MW		61	61
MGE Power Elm Road [Member]
Significant Balance Sheet Accounts Related to Interests in Variable Interest Entities
Property, plant, and equipment, net		$ 177,904	$ 179,620
Construction work in progress		2,400	1,976
Affiliate receivables, current and noncurrent		0	1,742
Deferred income taxes		40,865	40,044
Long-term debt, gross, current and noncurrent		65,305	67,972
Noncontrolling interest	[1]	79,113	72,537
Total carrying costs		62,500
Total capitalized interest		17,000
Total capitalized cost of equity		$ 45,500
Carrying cost rate recovery period		6 years
MGE Power Elm Road [Member] | Minimum [Member]
Significant Balance Sheet Accounts Related to Interests in Variable Interest Entities
Debt service coverage ratio		1.25
MGE Power West Campus [Member]
Significant Balance Sheet Accounts Related to Interests in Variable Interest Entities
Property, plant, and equipment, net		$ 84,403	86,763
Affiliate receivables, current and noncurrent		5,295	5,862
Deferred income taxes		19,612	23,813
Long-term debt, gross, current and noncurrent		46,703	48,218
Noncontrolling interest	[1]	37,603	$ 30,755
Carrying costs recovered		$ 12,100
Carrying cost rate recovery period		10 years
MGE Power West Campus [Member] | Minimum [Member]
Significant Balance Sheet Accounts Related to Interests in Variable Interest Entities
Debt service coverage ratio		1.25
MGE Power West Campus [Member] | Maximum [Member]
Significant Balance Sheet Accounts Related to Interests in Variable Interest Entities
Debt to total capitalization ratio		0.65

[1] 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.