Schedule I - Condensed Parent Company Finanical Statements (Details-Balance Sheet) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Assets, Current [Abstract]
Cash and cash equivalents	$ 11,604	$ 17,438
Other current assets	19,017	11,183
Total Current Assets	243,480	199,371
Other deferred assets and other
Other deferred assets and other	23,809	27,548
Investments:
Other investments	2,298	2,324
Total investments	105,883	98,754
Total Assets	2,517,600	2,371,906	$ 2,253,651
Current Liabilities:
Other current liabilities	8,057	10,608
Total Current Liabilities	225,062	117,847
Other Credits:
Deferred income taxes	252,190	231,149
Other deferred liabilities and other	96,990	91,690
Total Other Credits	625,618	612,380
Shareholders' Equity:
Retained earnings	649,854	596,402
Total Common Shareholders' Equity	1,081,674	1,027,468	$ 976,000	$ 855,676
Commitments and contingencies (see Footnote 3)
Total Liabilities and Capitalization	2,517,600	2,371,906
MGE Energy [Member]
Assets, Current [Abstract]
Cash and cash equivalents	3,336	6,959
Other current assets	1,978	1,681
Total Current Assets	5,314	8,640
Other deferred assets and other
Other deferred assets and other	294	244
Investments:
Investments in affiliates	1,091,103	1,036,347
Other investments	21,193	18,927
Total investments	1,112,296	1,055,274
Total Assets	1,117,904	1,064,158
Current Liabilities:
Accounts payable to affiliates	530	548
Other current liabilities	2,017	2,516
Total Current Liabilities	2,547	3,064
Other Credits:
Deferred income taxes	32,624	32,014
Accounts payable to affiliates	1,059	1,589
Other deferred liabilities and other	0	23
Total Other Credits	33,683	33,626
Shareholders' Equity:
Common shareholders' equity	431,820	431,066
Retained earnings	649,854	596,402
Total Common Shareholders' Equity	1,081,674	1,027,468
Commitments and contingencies (see Footnote 3)
Total Liabilities and Capitalization	$ 1,117,904	$ 1,064,158