Asset Retirement Obligations (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Asset Retirement Obligations [Roll Forward]
Asset retirement obligation, beginning balance	$ 18,768,000	$ 19,173,000
Liabilities incurred	296,000	49,000
Accretion expense	1,015,000	1,021,000
Liabilities settled	(744,000)	(221,000)
Revisions in estimated cash flows	24,000	(1,254,000)	[1]
Asset retirement obligation, ending balance	19,359,000	18,768,000
Revisions in estimated cash flows [Abstract]
Decrease in revisions in estimated cash flows for revised asbestos abatement related to the asset retirement obligation	$ 0	$ (1,300,000)

[1] (a) In 2012, MGE recorded a decrease in revisions in estimated cash flows of $1.3 million based on revised asbestos abatement estimates.