Schedule I - Condensed Parent Company Finanical Statements (Details-Balance Sheet) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Assets, Current [Abstract]
Cash and cash equivalents	$ 11,140	$ 11,604
Other current assets	15,587	19,017
Total Current Assets	238,197	243,480
Other deferred assets and other
Other deferred assets and other	20,741	24,365
Investments:
Other investments	2,298	2,298
Total investments	112,823	105,883
Total Assets	2,675,458	2,517,600	$ 2,371,906
Current Liabilities:
Accounts payable to affiliates, current	65,451	59,334
Other current liabilities	8,003	8,057
Total Current Liabilities	157,156	225,062
Other Credits:
Deferred income taxes	279,029	252,190
Other deferred liabilities and other	43,643	46,730
Total Other Credits	659,407	625,618
Shareholders' Equity:
Retained earnings	707,160	649,854
Total Common Shareholders' Equity	1,140,073	1,081,674	$ 1,027,468	$ 976,000
Commitments and contingencies (see Footnote 3)
Total Liabilities and Capitalization	2,675,458	2,517,600
MGE Energy [Member]
Assets, Current [Abstract]
Cash and cash equivalents	4,353	3,336
Other current assets	2,395	1,978
Total Current Assets	6,748	5,314
Other deferred assets and other
Other deferred assets and other	210	294
Investments:
Investments in affiliates	1,148,134	1,091,103
Other investments	21,714	21,193
Total investments	1,169,848	1,112,296
Total Assets	1,176,806	1,117,904
Current Liabilities:
Accounts payable to affiliates, current	572	530
Other current liabilities	1,650	2,017
Total Current Liabilities	2,222	2,547
Other Credits:
Deferred income taxes	33,974	32,624
Accounts payable to affiliates	529	1,059
Other deferred liabilities and other	8	0
Total Other Credits	34,511	33,683
Shareholders' Equity:
Common shareholders' equity	432,913	431,820
Retained earnings	707,160	649,854
Total Common Shareholders' Equity	1,140,073	1,081,674
Commitments and contingencies (see Footnote 3)
Total Liabilities and Capitalization	$ 1,176,806	$ 1,117,904