Schedule I - Condensed Parent Company Finanical Statements (Details-Balance Sheet) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Current Assets:
Cash and cash equivalents	$ 95,959	$ 81,384		$ 65,755		$ 68,813
Accounts receivable, net:
Other current assets	12,293	10,570
Total Current Assets	275,515	254,751
Other deferred assets and other	1,088	1,332	[1]
Investments:
Other investments	120	159
Total investments	76,290	73,631
Total Assets	1,801,060	1,726,403	[1]	1,689,521	[1]
Current Liabilities:
Other current liabilities	19,456	4,910
Total Current Liabilities	103,505	84,146
Other Credits:
Deferred income taxes	383,813	360,785
Total Other Credits	590,676	565,055
Shareholders' Equity:
Retained income	372,950	339,165
Other comprehensive income	202	357
Total Common Shareholders' Equity	724,088	690,458		659,401		617,510
Commitments and contingencies (see Footnote 3)
Total Liabilities and Capitalization	1,801,060	1,726,403	[1]
MGE Energy [Member]
Current Assets:
Cash and cash equivalents	82,225	51,781		$ 58,429		$ 51,204
Accounts receivable, net:
Accounts receivable from affiliates	83	20
Other current assets	1,221	1,386
Total Current Assets	83,529	53,187
Other deferred assets and other	201	249
Investments:
Investments in affiliates	684,968	649,276
Other investments	1,161	1,447
Total investments	686,129	650,723
Total Assets	769,859	704,159
Current Liabilities:
Accounts payable to affiliates	530	530
Accrued taxes	218	263
Other current liabilities	115	144
Total Current Liabilities	863	937
Other Credits:
Deferred income taxes	40,672	7,998
Accounts payable to affiliates	4,236	4,766
Total Other Credits	44,908	12,764
Shareholders' Equity:
Common shareholders' equity	350,936	350,936
Retained income	372,950	339,165
Other comprehensive income	202	357
Total Common Shareholders' Equity	724,088	690,458
Commitments and contingencies (see Footnote 3)
Total Liabilities and Capitalization	$ 769,859	$ 704,159

[1] Reflects retrospective application of new accounting pronouncement. See Footnote 19 for additional information.