Pension Plans and Other Postretirement Benefits (Details-1) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Defined Benefit Plan, Deferred Pension and Other Postretirement Benefit Plan Costs Recovered [Abstract]
Defined Contribution Plan, Cost		$ 6,900	$ 6,500	$ 5,200
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets as of January 1		465,789
Fair value of plan assets as of December 31		505,260	465,789
Amounts recognized in the consolidated balance sheets to reflect funded status of plans [Abstract]
Long-term asset		164,985	132,264
Long-term liability		(51,105)	(50,155)
Pension Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Net benefit obligation as of January 1		326,937	346,460
Service cost		2,612	3,078	2,892
Interest cost		17,139	17,118	17,319
Plan participants' contributions		0	0
Actuarial loss (gain)	[1]	11,028	(16,669)
Settlements	[2]	0	0
Gross benefits paid		(22,239)	(23,050)
Less: federal subsidy on benefits paid	[3]	0	0
Benefit obligation as of December 31		335,477	326,937	346,460
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets as of January 1		424,468	404,735
Actual return in plan assets		57,886	40,608
Employer contributions		2,304	2,175
Plan participants' contributions		0	0
Settlements		0	0
Gross benefits paid		(22,239)	(23,050)
Fair value of plan assets as of December 31		462,419	424,468	404,735
Funded Status as of December 31		126,942	97,531
Accumulated benefit obligation		318,800	311,000
Amounts recognized in the consolidated balance sheets to reflect funded status of plans [Abstract]
Long-term asset		162,493	131,418
Current liability		(2,477)	(2,441)
Long-term liability		(33,074)	(31,446)
Net asset (liability)		126,942	97,531
Amounts recognized in the consolidated balance sheets as regulatory asset [Abstract]
Net actuarial loss (gain)		(14,444)	3,699
Transition obligation		0	0
Total		(14,444)	3,699
Projected benefit obligation in excess of plan assets [Abstract]
Projected benefit obligation with projected benefit obligation in excess of plan assets, end of year		35,551	33,887
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		33,553	32,463
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		59,184	64,973
Service cost		743	856	780
Interest cost		3,028	3,126	3,308
Plan participants' contributions		1,081	1,045
Actuarial loss (gain)	[1]	289	(3,769)
Settlements	[2]	0	(1,227)
Gross benefits paid		(6,299)	(6,171)
Less: federal subsidy on benefits paid	[3]	354	351
Benefit obligation as of December 31		58,380	59,184	64,973
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets as of January 1		41,321	43,149
Actual return in plan assets		5,999	4,131
Employer contributions		739	682
Plan participants' contributions		1,081	1,045
Settlements		0	(1,515)
Gross benefits paid		(6,299)	(6,171)
Fair value of plan assets as of December 31		42,841	41,321	$ 43,149
Funded Status as of December 31		(15,539)	(17,863)
Medicare subsidy due to MGE		300	300
Amounts recognized in the consolidated balance sheets to reflect funded status of plans [Abstract]
Long-term asset		2,492	846
Current liability		0	0
Long-term liability		(18,031)	(18,709)
Net asset (liability)		(15,539)	(17,863)
Amounts recognized in the consolidated balance sheets as regulatory asset [Abstract]
Net actuarial loss (gain)		(9,575)	(7,191)
Transition obligation		0	3
Total		(9,575)	(7,188)
Accumulated benefit obligation in excess of plan assets [Abstract]
Accumulated benefit obligation with accumulated benefit obligation in excess of plan assets, end of year		44,007	43,882
Fair value of plan assets with accumulated benefit obligation in excess of plan assets, end of year		$ 25,976	$ 25,172

[1] Changes in discount rates were the primary driver of the actuarial loss (gain) in 2025 and 2024.

[2] In August 2024, MGE entered into an agreement to transfer the mortality and investment risk, as well as the administration of, its employer-paid life insurance plan to a third party. MGE accounted for the settlement under the scope of ASC 715.

[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, 2025 and 2024, the subsidy due to MGE was $0.3 million.