Pension Plans and Other Postretirement Benefits (Details-1) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
Defined contribution plans [Abstract]
Defined contribution costs	$ 2,300,000		$ 2,100,000	$ 1,800,000
Health care cost trend rates [Abstract]
Health care cost trend rate assumed for next year	7.00%		7.50%
Ultimate trend rate	5.00%		5.00%
Year that the rate reaches the ultimate trend rate	2018		2018
How 1% increase or decrease in health care cost trends could impact postretirement benefits [Abstract]
1% increase	1,286,000
1% decrease	(1,840,000)
Postretirement Medical Plans with Prescription Drug Benefits [Abstract]
Medicare subsidy due to MGE	200,000
Pension Benefits [Member]
Change in benefit obligations [Roll Forward]
Net benefit obligation at beginning of year	315,505,000		283,668,000
Service cost	7,705,000		7,139,000	6,013,000
Interest cost	12,656,000		12,704,000	12,281,000
Plan participants' contributions	0		0
Plan amendments	0		(912,000)
Actuarial (gain) loss	(40,335,000)		22,266,000
Special termination benefits	0		0	13,000
Gross benefits paid	(11,573,000)		(9,360,000)
Less: federal subsidy on benefits paid	0		0
Benefit obligation at end of year	283,958,000		315,505,000	283,668,000
Accumulated benefit obligation	254,500,000		272,500,000
Weighted-average assumptions used to determine benefit obligations [Abstract]
Discount rate	4.88%		4.09%
Rate of compensation increase	3.90%		4.60%
Postretirement Benefits [Member]
Change in benefit obligations [Roll Forward]
Net benefit obligation at beginning of year	92,605,000		97,644,000
Service cost	2,380,000		2,528,000	1,920,000
Interest cost	3,871,000		4,431,000	3,980,000
Plan participants' contributions	665,000		718,000
Plan amendments	(20,915,000)	[1]	0
Actuarial (gain) loss	(9,687,000)		(9,748,000)
Special termination benefits	0		0	0
Gross benefits paid	(2,998,000)		(3,155,000)
Less: federal subsidy on benefits paid	179,000		187,000
Benefit obligation at end of year	$ 66,100,000		$ 92,605,000	$ 97,644,000
Plan amendment, maximum percentage of 2013 employer contributions to be paid toward retiree medical premiums	175.00%
Weighted-average assumptions used to determine benefit obligations [Abstract]
Discount rate	4.69%		4.14%

[1] In 2013, MGE capped the amount it pays each year toward retiree medical premiums at 175% of the 2013 employer contribution for qualified employees.