Schedule I - Condensed Parent Company Finanical Statements (Details-Balance Sheet) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Assets, Current [Abstract]
Cash and cash equivalents	$ 5,666	$ 21,302
Other current assets	17,201	14,229
Total Current Assets	228,548	227,265
Other deferred assets and other
Other deferred assets and other	18,348	26,285
Investments:
Other investments	2,298	2,298
Total investments	127,913	118,035
Total Assets	3,155,420	2,827,959
Current Liabilities:
Accounts payable to affiliates, current	117,673	77,466
Other current liabilities	11,873	7,418
Total Current Liabilities	296,709	125,563
Other Credits:
Deferred income taxes	337,798	316,397
Other deferred liabilities and other	63,397	64,553
Total Other Credits	762,570	708,561
Shareholders' Equity:
Retained earnings	832,435	764,133
Total Common Shareholders' Equity	1,303,936	1,230,138	$ 1,140,073	$ 1,081,674
Commitments and contingencies (see Footnote 3)
Total Liabilities and Capitalization	3,155,420	2,827,959
MGE Energy [Member]
Assets, Current [Abstract]
Cash and cash equivalents	2,298	3,195
Other current assets	3,830	3,284
Total Current Assets	6,128	6,479
Other deferred assets and other
Other deferred assets and other	117	163
Investments:
Investments in affiliates	1,314,778	1,236,884
Other investments	22,227	22,785
Total investments	1,337,005	1,259,669
Total Assets	1,343,250	1,266,311
Current Liabilities:
Accounts payable to affiliates, current	63	591
Other current liabilities	2,515	14
Total Current Liabilities	2,578	605
Other Credits:
Deferred income taxes	36,720	35,559
Other deferred liabilities and other	16	9
Total Other Credits	36,736	35,568
Shareholders' Equity:
Common shareholders' equity	471,501	466,005
Retained earnings	832,435	764,133
Total Common Shareholders' Equity	1,303,936	1,230,138
Commitments and contingencies (see Footnote 3)
Total Liabilities and Capitalization	$ 1,343,250	$ 1,266,311