Pension Plans and Other Postretirement Benefits (Details-1) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan, Deferred Pension and Other Postretirement Benefit Plan Costs Recovered [Abstract]
Defined Contribution Plan, Cost		$ 5,200	$ 5,400	$ 5,100
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets as of January 1		412,038
Fair value of plan assets as of December 31		447,884	412,038
Amounts recognized in the consolidated balance sheets to reflect funded status of plans [Abstract]
Long-term asset		93,896	68,872
Long-term liability		(55,058)	(53,607)
Pension Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Net benefit obligation as of January 1		335,288	460,666
Service cost		2,892	5,064	5,730
Interest cost		17,319	11,161	9,109
Plan participants' contributions		0	0
Actuarial loss (gain)	[1]	11,946	(120,166)
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment		0	0
Gross benefits paid		(20,985)	(21,437)
Less: federal subsidy on benefits paid	[2]	0	0
Benefit obligation as of December 31		346,460	335,288	460,666
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets as of January 1		370,171	473,953
Actual return in plan assets		53,346	(84,562)
Employer contributions		2,203	2,217
Plan participants' contributions		0	0
Gross benefits paid		(20,985)	(21,437)
Fair value of plan assets as of December 31		404,735	370,171	473,953
Funded Status as of December 31		58,275	34,883
Accumulated benefit obligation		328,400	319,600
Amounts recognized in the consolidated balance sheets to reflect funded status of plans [Abstract]
Long-term asset		93,896	68,872
Current liability		(2,387)	(2,408)
Long-term liability		(33,234)	(31,581)
Net asset (liability)		58,275	34,883
Amounts recognized in the consolidated balance sheets as regulatory asset [Abstract]
Net actuarial loss (gain)		33,237	51,148
Prior service (credit) cost		0	0
Transition obligation		0	0
Total		33,237	51,148
Projected benefit obligation in excess of plan assets [Abstract]
Projected benefit obligation with projected benefit obligation in excess of plan assets, end of year		35,621	33,989
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		34,387	33,211
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		63,828	84,526
Service cost		780	1,293	1,448
Interest cost		3,308	1,940	1,549
Plan participants' contributions		1,017	986
Actuarial loss (gain)	[1]	1,951	(19,484)
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment		(242)	0
Gross benefits paid		(5,986)	(5,725)
Less: federal subsidy on benefits paid	[2]	317	292
Benefit obligation as of December 31		64,973	63,828	84,526
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets as of January 1		41,867	54,844
Actual return in plan assets		5,312	(8,958)
Employer contributions		939	720
Plan participants' contributions		1,017	986
Gross benefits paid		(5,986)	(5,725)
Fair value of plan assets as of December 31		43,149	41,867	$ 54,844
Funded Status as of December 31		(21,824)	(21,961)
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		(21,824)	(21,961)
Net asset (liability)		(21,824)	(21,961)
Amounts recognized in the consolidated balance sheets as regulatory asset [Abstract]
Net actuarial loss (gain)		(1,626)	(1,085)
Prior service (credit) cost		(242)	0
Transition obligation		5	9
Total		(1,863)	(1,076)
Accumulated benefit obligation in excess of plan assets [Abstract]
Accumulated benefit obligation with accumulated benefit obligation in excess of plan assets, end of year		64,973	63,828
Fair value of plan assets with accumulated benefit obligation in excess of plan assets, end of year		$ 43,149	$ 41,867

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

[2] 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, 2023 and 2022, the subsidy due to MGE was $0.3 million.