Schedule I - Condensed Parent Company Finanical Statements (Details-Balance Sheet) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Current Assets:
Cash and cash equivalents	$ 41,169	$ 7,110	$ 4,704	$ 4,106
Accounts receivable, net:
Prepaid taxes and other	22,251	22,496
Total Current Assets	189,131	162,302
Other deferred assets and other	6,524	8,641
Investments:
Other	1,802	0
Total investments	60,332	55,845
Total Assets	1,458,882	1,317,893	1,281,885
Current Liabilities:
Short-term debt	0	22,500	64,500
Other current liabilities	8,783	9,577
Total Current Liabilities	63,074	81,212
Other Credits:
Deferred income taxes	199,850	166,774
Total Other Credits	483,953	377,250
Shareholders' Equity
Retained income	211,458	185,556
Other comprehensive income/(loss)	112	142
Total Capitalization	911,855	859,431
Commitments and contingencies (see Footnote 18)	0	0
Total Liabilities and Capitalization	1,458,882	1,317,893
MGE Energy [Member]
Current Assets:
Cash and cash equivalents	24,620	972	568	870
Accounts receivable, net:
Accounts receivable from affiliates	2,148	58
Prepaid taxes and other	481	1,161
Total Current Assets	27,249	2,191
Other deferred assets and other	151	163
Investments:
Investments in affiliates	534,009	551,818
Other	567	483
Total investments	534,576	552,301
Total Assets	561,976	554,655
Current Liabilities:
Short-term debt	0	19,000
Accounts payable to affiliates	602	630
Other current liabilities	218	141
Total Current Liabilities	820	19,771
Other Credits:
Deferred income taxes	3,320	2,391
Accounts payable to affiliates	6,884	7,413
Total Other Credits	10,204	9,804
Shareholders' Equity
Common shareholders equity	339,382	339,382
Retained income	211,458	185,556
Other comprehensive income/(loss)	112	142
Total Capitalization	550,952	525,080
Commitments and contingencies (see Footnote 18)	0	0
Total Liabilities and Capitalization	$ 561,976	$ 554,655