Schedule I - Condensed Parent Company Finanical Statements (Details-Balance Sheet) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Current Assets:
Cash and cash equivalents	$ 23,481,000	$ 83,102,000
Other current assets	10,233,000	8,593,000
Total Current Assets	181,641,000	240,560,000
Other deferred assets and other
Other deferred assets and other	19,093,000	12,488,000
Investments:
Other investments	2,298,000	2,298,000
Total investments	88,492,000	78,000,000
Total Assets	2,081,664,000	1,988,618,000	$ 1,855,182,000	[1]
Current Liabilities:
Other current liabilities	14,676,000	14,113,000
Total Current Liabilities	128,820,000	120,628,000
Other Credits:
Deferred income taxes	243,302,000	231,952,000
Other deferred liabilities and other	63,013,000	66,361,000
Total Other Credits	573,427,000	558,003,000
Shareholders' Equity:
Retained earnings	504,740,000	465,708,000
Total Common Shareholders' Equity	855,676,000	816,644,000	$ 778,187,000		$ 724,088,000
Commitments and contingencies (see Footnote 3)
Total Liabilities and Capitalization	2,081,664,000	1,988,618,000
MGE Energy [Member]
Current Assets:
Cash and cash equivalents	17,182,000	75,036,000
Other current assets	3,180,000	3,646,000
Total Current Assets	20,362,000	78,682,000
Other deferred assets and other
Other deferred assets and other	498,000	110,000
Investments:
Investments in affiliates	856,444,000	763,625,000
Other investments	12,910,000	7,672,000
Total investments	869,354,000	771,297,000
Total Assets	890,214,000	850,089,000
Current Liabilities:
Accounts payable to affiliates	530,000	617,000
Other current liabilities	2,314,000	2,500,000
Total Current Liabilities	2,844,000	3,117,000
Other Credits:
Deferred income taxes	29,006,000	27,151,000
Accounts payable to affiliates	2,647,000	3,177,000
Other deferred liabilities and other	41,000	0
Total Other Credits	31,694,000	30,328,000
Shareholders' Equity:
Common shareholders' equity	350,936,000	350,936,000
Retained earnings	504,740,000	465,708,000
Total Common Shareholders' Equity	855,676,000	816,644,000
Commitments and contingencies (see Footnote 3)
Total Liabilities and Capitalization	$ 890,214,000	$ 850,089,000

[1] In December 2017, there was a $20.4 million one-time tax impact as a result of the Tax Act.