Pension Plans and Other Postretirement Benefits (Details-1) - USD ($)		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan, Deferred Pension and Other Postretirement Benefit Plan Costs Recovered [Abstract]
Defined contribution costs		$ 5,100,000	$ 4,700,000	$ 4,400,000
Change in plan assets [Roll Forward]
Fair value of plan assets as of January 1		481,273,000
Fair value of plan assets as of December 31		528,797,000	481,273,000
Amounts recognized in the consolidated balance sheets to reflect funded status of plans [Abstract]
Long-term asset		58,757,000	13,873,000
Long-term liability		(73,085,000)	(78,168,000)
Pension Benefits [Member]
Change in benefit obligations [Roll Forward]
Net benefit obligation as of January 1		461,215,000	410,651,000
Service cost	[1]	5,730,000	5,296,000	4,692,000
Interest cost	[1]	9,109,000	12,210,000	14,302,000
Plan participants' contributions		0	0
Actuarial loss (gain)	[2]	(3,871,000)	(50,325,000)
Gross benefits paid		(19,259,000)	(17,267,000)
Less: federal subsidy on benefits paid	[3]	0	0
Benefit obligation as of December 31		460,666,000	461,215,000	410,651,000
Change in plan assets [Roll Forward]
Fair value of plan assets as of January 1		429,538,000	386,033,000
Actual return on plan assets		61,487,000	58,935,000
Employer contributions		2,187,000	1,837,000
Plan participant contributions		0	0
Gross benefits paid		(19,259,000)	(17,267,000)
Fair value of plan assets as of December 31		473,953,000	429,538,000	386,033,000
Funded Status as of December 31		13,287,000	(31,677,000)
Accumulated benefit obligation		431,300,000	430,300,000
Amounts recognized in the consolidated balance sheets to reflect funded status of plans [Abstract]
Long-term asset		58,757,000	13,873,000
Current liability		(2,342,000)	(2,139,000)
Long-term liability		(43,128,000)	(43,411,000)
Net liability		13,287,000	(31,677,000)
Amounts recognized in the consolidated balance sheets as regulatory asset [Abstract]
Net actuarial loss		57,777,000	92,553,000
Prior service (credit) cost		(20,000)	(144,000)
Transition obligation		0	0
Total		57,757,000	92,409,000
Projected benefit obligation in excess of plan assets [Abstract]
Projected benefit obligation with projected benefit obligation in excess of plan assets, end of year		45,470,000	45,550,000
Fair value of plan assets with projected benefit obligation in excess of plan assets, end of year		0	0
Accumulated benefit obligation in excess of plan assets [Abstract]
Accumulated benefit obligation with accumulated benefit obligation in excess of plan assets, end of year		43,831,000	43,384,000
Fair value of plan assets with accumulated benefit obligation in excess of plan assets, end of year		0	0
Postretirement Benefits [Member]
Change in benefit obligations [Roll Forward]
Net benefit obligation as of January 1		86,360,000	80,901,000
Service cost	[1]	1,448,000	1,264,000	1,110,000
Interest cost	[1]	1,549,000	2,278,000	2,893,000
Plan participants' contributions		992,000	1,009,000
Actuarial loss (gain)	[2]	685,000	(5,907,000)
Gross benefits paid		(5,405,000)	(5,245,000)
Less: federal subsidy on benefits paid	[3]	267,000	246,000
Benefit obligation as of December 31		84,526,000	86,360,000	80,901,000
Change in plan assets [Roll Forward]
Fair value of plan assets as of January 1		51,735,000	48,889,000
Actual return on plan assets		6,814,000	6,514,000
Employer contributions		708,000	568,000
Plan participant contributions		992,000	1,009,000
Gross benefits paid		(5,405,000)	(5,245,000)
Fair value of plan assets as of December 31		54,844,000	51,735,000	$ 48,889,000
Funded Status as of December 31		(29,682,000)	(34,625,000)
Medicare subsidy due to MGE		300,000	200,000
Amounts recognized in the consolidated balance sheets to reflect funded status of plans [Abstract]
Long-term asset		0	0
Current liability		0	0
Long-term liability		(29,682,000)	(34,625,000)
Net liability		(29,682,000)	(34,625,000)
Amounts recognized in the consolidated balance sheets as regulatory asset [Abstract]
Net actuarial loss		6,256,000	10,986,000
Prior service (credit) cost		(297,000)	(1,816,000)
Transition obligation		12,000	15,000
Total		5,971,000	9,185,000
Accumulated benefit obligation in excess of plan assets [Abstract]
Accumulated benefit obligation with accumulated benefit obligation in excess of plan assets, end of year		84,526,000	86,360,000
Fair value of plan assets with accumulated benefit obligation in excess of plan assets, end of year		$ 54,844,000	$ 51,735,000

[1] During 2019, MGE deferred approximately $6.2 million of pension and other postretirement costs. During 2021 and 2020, MGE collected approximately $4.3 million and $0.9 million, respectively, of pension and other postretirement costs, which reduced the amount deferred in prior years. The impact of the deferral has not been reflected in the table above. See Footnote 8 for further information. During the year ended December 30, 2021, MGE deferred $8.1 million of savings from 2021 employee benefit plan costs and recorded as a regulatory liability. The deferred savings has not been reflected in the table above. See Footnote 8 for additional information.

[2] In 2020, lower discount rates were the primary driver of the actuarial loss.

[3] In 2003, the Medicare Prescription Drug, Improvement and Modernization Act of 2003 was signed into law authorizing Medicare to provide prescription drug benefits to retirees. For the years ended December 31, 2021 and 2020, the subsidy due to MGE was $0.3 million and $0.2 million, respectively.