Schedule I - Condensed Parent Company Finanical Statements (Details-Balance Sheet) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current Assets:
Cash and cash equivalents	$ 68,813	$ 46,357	$ 41,169	$ 7,110
Accounts receivable, net:
Prepaid taxes and other	19,106	19,520
Total Current Assets	220,601	222,937
Other deferred assets and other	5,853	5,973
Investments:
Other investments	0	1,804
Total investments	67,952	64,595
Total Assets	1,579,060	1,586,924	1,458,882
Current Liabilities:
Accrued interest and taxes	5,661	4,296
Other current liabilities	9,489	5,637
Total Current Liabilities	96,666	75,797
Other Credits:
Deferred income taxes	284,791	270,410
Total Other Credits	465,470	573,207
Shareholders' Equity:
Retained income	266,197	228,399
Other comprehensive income (loss)	377	94
Total Common Shareholders' Equity	617,510	579,429	550,952	525,080
Commitments and contingencies (see Footnote 18)	0	0
Total Liabilities and Capitalization	1,579,060	1,586,924
MGE Energy [Member]
Current Assets:
Cash and cash equivalents	51,204	36,881	24,620	972
Accounts receivable, net:
Accounts receivable from affiliates	125	795
Prepaid taxes and other	1,015	451
Total Current Assets	52,344	38,127
Other deferred assets and other	157	129
Investments:
Investments in affiliates	583,435	556,911
Other investments	948	787
Total investments	584,383	557,698
Total Assets	636,884	595,954
Current Liabilities:
Accounts payable to affiliates	530	603
Accrued interest and taxes	4,297	4,164
Other current liabilities	3,076	1,148
Total Current Liabilities	7,903	5,915
Other Credits:
Deferred income taxes	5,646	4,228
Accounts payable to affiliates	5,825	6,382
Total Other Credits	11,471	10,610
Shareholders' Equity:
Common shareholders' equity	350,936	350,936
Retained income	266,197	228,399
Other comprehensive income (loss)	377	94
Total Common Shareholders' Equity	617,510	579,429
Commitments and contingencies (see Footnote 18)	0	0
Total Liabilities and Capitalization	$ 636,884	$ 595,954