Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Current Assets:
Cash and cash equivalents	$ 59,203		$ 41,169
Receivable - margin account	1,653		2,477
Accounts receivable, less reserves	33,315	[1]	36,744	[2]
Other accounts receivables, less reserves	4,621	[3]	5,318	[4]
Unbilled revenues	19,095		25,754
Materials and supplies, at average cost	17,014		14,758
Fossil fuel	6,863		5,468
Stored natural gas, at average cost	17,218		19,575
Prepaid taxes	43,590		22,251
Regulatory assets - current	8,350		7,347
Other current assets	8,885		8,270
Total Current Assets	219,807		189,131
Regulatory assets	230,418		205,835
Other deferred assets and other	7,298		8,018
Property, Plant, and Equipment:
Property, plant, and equipment, net	967,556		961,511
Construction work in progress	75,748		34,055
Total Property, Plant, and Equipment	1,043,304		995,566
Investments	63,829		60,332
Total Assets	1,564,656		1,458,882
Current Liabilities:
Long-term debt due within one year	2,667		2,667
Accounts payable	29,238		34,532
Accrued interest and taxes	4,064		4,085
Accrued payroll related items	9,409		9,987
Deferred income taxes	1,577		3,020
Derivative liabilities	9,600		4,568
Other current liabilities	3,421		4,215
Total Current Liabilities	59,976		63,074
Other Credits:
Deferred income taxes	256,689		199,850
Investment tax credit - deferred	1,585		1,780
Regulatory liabilities	25,817		20,463
Accrued pension and other postretirement benefits	166,788		183,622
Derivative liabilities	67,490		34,908
Other deferred liabilities and other	48,685		43,330
Total Other Credits	567,054		483,953
Capitalization:
Common shareholders equity	578,127		550,952
Long-term debt	359,499		360,903
Total Capitalization	937,626		911,855
Commitments and contingencies (see Footnote 8)	0		0
Total Liabilities and Capitalization	1,564,656		1,458,882
MGE [Member]
Current Assets:
Cash and cash equivalents	29,536		13,898
Receivable - margin account	1,653		2,477
Accounts receivable, less reserves	32,621	[1]	35,765	[2]
Affiliate receivables	572		605
Other accounts receivables, less reserves	4,606	[3]	5,301	[4]
Unbilled revenues	19,095		25,754
Materials and supplies, at average cost	17,014		14,758
Fossil fuel	6,863		5,468
Stored natural gas, at average cost	17,218		19,575
Prepaid taxes	44,515		21,977
Regulatory assets - current	8,350		7,347
Other current assets	8,851		8,245
Total Current Assets	190,894		161,170
Affiliate receivable long-term	6,487		6,884
Regulatory assets	230,418		205,835
Other deferred assets and other	6,721		7,286
Property, Plant, and Equipment:
Property, plant, and equipment, net	967,052		961,007
Construction work in progress	75,748		34,055
Total Property, Plant, and Equipment	1,042,800		995,062
Investments	60,743		57,556
Total Assets	1,538,063		1,433,793
Current Liabilities:
Long-term debt due within one year	2,667		2,667
Accounts payable	29,238		34,532
Affiliate payables	1,143		2,152
Accrued interest and taxes	4,017		4,037
Accrued payroll related items	9,409		9,987
Deferred income taxes	1,646		3,020
Derivative liabilities	9,600		4,568
Other current liabilities	3,577		3,997
Total Current Liabilities	61,297		64,960
Other Credits:
Deferred income taxes	252,656		196,550
Investment tax credit - deferred	1,585		1,780
Regulatory liabilities	25,817		20,463
Accrued pension and other postretirement benefits	166,788		183,622
Derivative liabilities	67,490		34,908
Other deferred liabilities and other	48,685		43,330
Total Other Credits	563,021		480,653
Capitalization:
Common shareholders equity	435,315		412,926
Noncontrolling interest	118,931		114,351
Total Equity	554,246		527,277
Long-term debt	359,499		360,903
Total Capitalization	913,745		888,180
Commitments and contingencies (see Footnote 8)	0		0
Total Liabilities and Capitalization	$ 1,538,063		$ 1,433,793

[1] less reserves of $3,516

[2] less reserves of $3,662

[3] less reserves of $611

[4] less reserves of $439