Pension Plans and Other Postretirement Benefits (Details-1) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan, Deferred Pension and Other Postretirement Benefit Plan Costs Recovered [Abstract]
Defined Contribution Plan, Cost		$ 5,400	$ 5,100	$ 4,700
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets as of January 1		528,797
Fair value of plan assets as of December 31		412,038	528,797
Amounts recognized in the consolidated balance sheets to reflect funded status of plans [Abstract]
Long-term asset		68,872	58,757
Long-term liability		(53,607)	(73,085)
Pension Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Net benefit obligation as of January 1		460,666	461,215
Service cost	[1]	5,064	5,730	5,296
Interest cost	[1]	11,161	9,109	12,210
Plan participants' contributions		0	0
Actuarial loss (gain)	[2]	(120,166)	3,871
Gross benefits paid		(21,437)	(19,259)
Less: federal subsidy on benefits paid	[3]	0	0
Benefit obligation as of December 31		335,288	460,666	461,215
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets as of January 1		473,953	429,538
Actual return in plan assets		(84,562)	61,487
Employer contributions		2,217	2,187
Plan participants' contributions		0	0
Gross benefits paid		(21,437)	(19,259)
Fair value of plan assets as of December 31		370,171	473,953	429,538
Funded Status as of December 31		34,883	13,287
Accumulated benefit obligation		319,600	431,300
Amounts recognized in the consolidated balance sheets to reflect funded status of plans [Abstract]
Long-term asset		68,872	58,757
Current liability		(2,408)	(2,342)
Long-term liability		(31,581)	(43,128)
Net asset (liability)		34,883	13,287
Amounts recognized in the consolidated balance sheets as regulatory asset [Abstract]
Net actuarial loss (gain)		51,148	57,777
Prior service (credit) cost		(0)	(20)
Transition obligation		0	0
Total		51,148	57,757
Projected benefit obligation in excess of plan assets [Abstract]
Projected benefit obligation with projected benefit obligation in excess of plan assets, end of year		33,989	45,470
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		33,211	43,831
Fair value of plan assets with accumulated benefit obligation in excess of plan assets, end of year		0	0
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Net benefit obligation as of January 1		84,526	86,360
Service cost	[1]	1,293	1,448	1,264
Interest cost	[1]	1,940	1,549	2,278
Plan participants' contributions		986	992
Actuarial loss (gain)	[2]	(19,484)	(685)
Gross benefits paid		(5,725)	(5,405)
Less: federal subsidy on benefits paid	[3]	292	267
Benefit obligation as of December 31		63,828	84,526	86,360
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets as of January 1		54,844	51,735
Actual return in plan assets		(8,958)	6,814
Employer contributions		720	708
Plan participants' contributions		986	992
Gross benefits paid		(5,725)	(5,405)
Fair value of plan assets as of December 31		41,867	54,844	$ 51,735
Funded Status as of December 31		(21,961)	(29,682)
Medicare subsidy due to MGE		300	300
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		(21,961)	(29,682)
Net asset (liability)		(21,961)	(29,682)
Amounts recognized in the consolidated balance sheets as regulatory asset [Abstract]
Net actuarial loss (gain)		(1,085)	6,256
Prior service (credit) cost		(0)	(297)
Transition obligation		9	12
Total		(1,076)	5,971
Accumulated benefit obligation in excess of plan assets [Abstract]
Accumulated benefit obligation with accumulated benefit obligation in excess of plan assets, end of year		63,828	84,526
Fair value of plan assets with accumulated benefit obligation in excess of plan assets, end of year		$ 41,867	$ 54,844

[1] As approved by the PSCW, MGE is allowed to defer differences between actual employee benefit plan costs and costs reflected in current rates. The deferred costs may be recovered or refunded in MGE's next rate filing. For the years ended December 31, 2022, 2021, and 2020 MGE recovered approximately $1.0 million, $4.3 million, and $0.9 million, respectively, of pension and other postretirement costs. The recovery of these costs reduced the amount previously deferred and has not been reflected in the table above. See Footnote 8 for further information. For the years ended December 31, 2022 and 2021, MGE deferred and recorded as a regulatory liability $1.5 million and $8.1 million, respectively, of savings from employee benefit plan costs. For the year ended December 31, 2022, MGE refunded in rates $4.2 million of savings from 2021 employee benefit plan costs. The deferred savings has not been reflected in the table above. See Footnote 8 for additional information.

[2] In 2022, higher discount rates were the primary driver of the actuarial gain.

[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 both the years ended December 31, 2022 and 2021, the subsidy due to MGE was $0.3 million.