Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Current Assets:
Cash and cash equivalents	$ 41,169		$ 7,110
Receivable - margin account	2,477		2,501
Accounts receivable, less reserves	36,744	[1]	40,153	[2]
Other accounts receivables, less reserves	5,318	[3]	4,082	[4]
Unbilled revenues	25,754		29,220
Materials and supplies, at average cost	14,758		17,642
Fossil fuel	5,468		6,758
Stored natural gas, at average cost	19,575		22,839
Prepaid taxes	22,251		22,496
Regulatory assets - current	7,347		1,732
Other current assets	8,270		7,769
Total Current Assets	189,131		162,302
Other long-term receivables	1,494		2,013
Regulatory assets	205,835		121,085
Other deferred assets and other	6,524		8,641
Property, Plant, and Equipment:
Property, plant, and equipment, net	961,511		857,572
Construction work in progress	34,055		110,435
Total Property, Plant, and Equipment	995,566		968,007
Investments	60,332		55,845
Total Assets	1,458,882		1,317,893
Current Liabilities:
Long-term debt due within one year	2,667		1,667
Short-term debt	0		22,500
Accounts payable	34,532		32,555
Accrued interest and taxes	4,085		3,990
Accrued payroll related items	9,987		8,525
Deferred income taxes	3,020		2,398
Other current liabilities	8,783		9,577
Total Current Liabilities	63,074		81,212
Other Credits:
Deferred income taxes	199,850		166,774
Investment tax credit - deferred	1,780		2,081
Regulatory liabilities	20,463		23,772
Accrued pension and other postretirement benefits	183,622		123,648
Other deferred liabilities and other	78,238		60,975
Total Other Credits	483,953		377,250
Common shareholders' equity:
Common stock	23,114	[5]	23,114	[5]
Additional paid-in capital	316,268		316,268
Retained earnings	211,458		185,556
Accumulated other comprehensive income, net of tax	112		142
Total Common Shareholders' Equity	550,952		525,080
Long-term debt	360,903		334,351
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 [Member]
Current Assets:
Cash and cash equivalents	13,898		4,494
Receivable - margin account	2,477		2,501
Accounts receivable, less reserves	35,765	[1]	40,153	[2]
Affiliate receivables	605		638
Other accounts receivables, less reserves	5,301	[3]	4,063	[4]
Unbilled revenues	25,754		29,220
Materials and supplies, at average cost	14,758		17,642
Fossil fuel	5,468		6,758
Stored natural gas, at average cost	19,575		22,839
Prepaid taxes	21,977		21,500
Regulatory assets - current	7,347		1,732
Other current assets	8,245		7,742
Total Current Assets	161,170		159,282
Other long-term receivables	914		1,367
Affiliate receivable long-term	6,884		7,413
Regulatory assets	205,835		121,085
Other deferred assets and other	6,372		6,970
Property, Plant, and Equipment:
Property, plant, and equipment, net	961,007		857,442
Construction work in progress	34,055		110,435
Total Property, Plant, and Equipment	995,062		967,877
Investments	57,556		54,947
Total Assets	1,433,793		1,318,941
Current Liabilities:
Long-term debt due within one year	2,667		1,667
Short-term debt	0		3,500
Accounts payable	34,532		32,524
Affiliate payables	2,152		24
Accrued interest and taxes	4,037		7,294
Accrued payroll related items	9,987		8,525
Deferred income taxes	3,020		2,398
Other current liabilities	8,565		9,472
Total Current Liabilities	64,960		65,404
Other Credits:
Deferred income taxes	196,550		164,399
Investment tax credit - deferred	1,780		2,081
Regulatory liabilities	20,463		23,772
Accrued pension and other postretirement benefits	183,622		123,648
Other deferred liabilities and other	78,238		60,977
Total Other Credits	480,653		374,877
Common shareholders' equity:
Common stock	17,348	[6]	17,348	[6]
Additional paid-in capital	192,417		192,417
Retained earnings	203,114		192,480
Accumulated other comprehensive income, net of tax	47		71
Total Common Shareholders' Equity	412,926		402,316
Noncontrolling interest	114,351		141,993
Total Equity	527,277		544,309
Long-term debt	360,903		334,351
Total Capitalization	888,180		878,660
Commitments and contingencies (see Footnote 18)	0		0
Total Liabilities and Capitalization	$ 1,433,793		$ 1,318,941

[1] less reserves of $3,662

[2] less reserves of $3,994

[3] less reserves of $439

[4] less reserves of $595

[5] $1 par value - 50,000 shares authorized; 23,114 shares issued and outstanding

[6] $1 par value - 50,000 shares authorized; 17,348 shares outstanding