Consolidated Balance Sheets (Unaudited) (USD $) In Thousands	Sep. 30, 2011		Dec. 31, 2010
MGE Energy [Member]
Current Assets:
Cash and cash equivalents	$ 44,893		$ 7,110
Receivable - margin account	3,528		2,501
Accounts receivable, less reserves	35,115	[1]	40,153	[2]
Other accounts receivables, less reserves	4,157	[3]	4,082	[4]
Unbilled revenues	19,113		29,220
Materials and supplies, at average cost	17,103		17,642
Fossil fuel	5,817		6,758
Stored natural gas, at average cost	21,832		22,839
Prepaid taxes	11,209		22,496
Regulatory assets - current	2,866		1,732
Other current assets	8,030		7,769
Total Current Assets	173,663		162,302
Regulatory assets	121,337		121,085
Other deferred assets and other	11,546		10,654
Property, Plant, and Equipment:
Property, plant, and equipment, net	955,646		857,572
Construction work in progress	29,850		110,435
Total Property, Plant, and Equipment	985,496		968,007
Investments	59,873		55,845
Total Assets	1,351,915		1,317,893
Current Liabilities:
Long-term debt due within one year	2,667		1,667
Short-term debt	0		22,500
Accounts payable	26,381		32,555
Accrued interest and taxes	5,407		3,990
Accrued payroll related items	9,016		8,525
Deferred income taxes	1,732		2,398
Other current liabilities	7,278		9,577
Total Current Liabilities	52,481		81,212
Other Credits:
Deferred income taxes	184,668		166,774
Investment tax credit - deferred	1,855		2,081
Regulatory liabilities	21,146		23,772
Accrued pension and other postretirement benefits	107,640		123,648
Other deferred liabilities and other	72,136		60,975
Total Other Credits	387,445		377,250
Capitalization:
Common shareholders equity	550,433		525,080
Long-term debt	361,556		334,351
Total Capitalization	911,989		859,431
Commitments and contingencies (see Footnote 9)	0		0
Total Liabilities and Capitalization	1,351,915		1,317,893
MGE [Member]
Current Assets:
Cash and cash equivalents	26,497		4,494
Receivable - margin account	3,528		2,501
Accounts receivable, less reserves	34,179	[1]	40,153	[2]
Affiliate receivables	568		638
Other accounts receivables, less reserves	4,155	[3]	4,063	[4]
Unbilled revenues	19,113		29,220
Materials and supplies, at average cost	17,103		17,642
Fossil fuel	5,817		6,758
Stored natural gas, at average cost	21,832		22,839
Prepaid taxes	11,793		21,500
Regulatory assets - current	2,866		1,732
Other current assets	7,995		7,742
Total Current Assets	155,446		159,282
Affiliate receivable long-term	7,016		7,413
Regulatory assets	121,337		121,085
Other deferred assets and other	9,858		8,337
Property, Plant, and Equipment:
Property, plant, and equipment, net	955,144		857,442
Construction work in progress	29,850		110,435
Total Property, Plant, and Equipment	984,994		967,877
Investments	57,086		54,947
Total Assets	1,335,737		1,318,941
Current Liabilities:
Long-term debt due within one year	2,667		1,667
Short-term debt	0		3,500
Accounts payable	26,378		32,524
Affiliate payables	2,475		24
Accrued interest and taxes	6,397		7,294
Accrued payroll related items	9,016		8,525
Deferred income taxes	1,732		2,398
Other current liabilities	7,148		9,472
Total Current Liabilities	55,813		65,404
Other Credits:
Deferred income taxes	181,580		164,399
Investment tax credit - deferred	1,855		2,081
Regulatory liabilities	21,146		23,772
Accrued pension and other postretirement benefits	107,640		123,648
Other deferred liabilities and other	72,136		60,977
Total Other Credits	384,357		374,877
Capitalization:
Common shareholders equity	416,195		402,316
Noncontrolling interest	117,816		141,993
Total Equity	534,011		544,309
Long-term debt	361,556		334,351
Total Capitalization	895,567		878,660
Commitments and contingencies (see Footnote 9)	0		0
Total Liabilities and Capitalization	$ 1,335,737		$ 1,318,941

[1] less reserves of $3,868

[2] less reserves of $3,994

[3] less reserves of $476

[4] less reserves of $595