Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Current Assets:
Cash and cash equivalents	$ 93,489	$ 68,813
Accounts receivable, less reserves	62,760	44,890
Other accounts receivables, less reserves	5,019	5,352
Unbilled revenues	29,568	31,982
Materials and supplies, at average cost	17,023	16,662
Fossil fuel	4,675	5,206
Stored natural gas, at average cost	642	13,988
Prepaid taxes	11,773	19,106
Regulatory assets - current	4,690	6,377
Other current assets	9,301	8,225
Total Current Assets	238,940	220,601
Regulatory assets	105,253	107,166
Pension benefits	16,013	15,071
Other deferred assets and other	6,758	8,046
Property, Plant, and Equipment:
Property, plant, and equipment, net	1,026,807	1,018,809
Construction work in progress	147,449	141,415
Total Property, Plant, and Equipment	1,174,256	1,160,224
Investments	69,203	67,952
Total Assets	1,610,423	1,579,060
Current Liabilities:
Long-term debt due within one year	4,121	4,102
Accounts payable	56,171	43,684
Accrued taxes	11,275	822
Accrued interest	3,250	4,839
Accrued payroll related items	8,103	10,731
Deferred income taxes	0	1,711
Regulatory liabilities - current	11,537	13,538
Derivative liabilities	6,540	7,750
Other current liabilities	8,518	9,489
Total Current Liabilities	109,515	96,666
Other Credits:
Deferred income taxes	287,224	284,791
Investment tax credit - deferred	1,362	1,413
Regulatory liabilities	20,788	19,792
Accrued pension and other postretirement benefits	49,512	49,184
Derivative liabilities	53,750	57,930
Other deferred liabilities and other	54,155	52,360
Total Other Credits	466,791	465,470
Capitalization:
Common shareholders equity	635,734	617,510
Long-term debt	398,383	399,414
Total Capitalization	1,034,117	1,016,924
Commitments and contingencies (see Footnote 8)
Total Liabilities and Capitalization	1,610,423	1,579,060
MGE [Member]
Current Assets:
Cash and cash equivalents	37,988	14,808
Accounts receivable, less reserves	62,760	44,890
Affiliate receivables	550	534
Other accounts receivables, less reserves	4,937	5,274
Unbilled revenues	29,568	31,982
Materials and supplies, at average cost	17,023	16,662
Fossil fuel	4,675	5,206
Stored natural gas, at average cost	642	13,988
Prepaid taxes	12,044	23,934
Regulatory assets - current	4,690	6,377
Other current assets	8,979	8,197
Total Current Assets	183,856	171,852
Affiliate receivable long-term	5,692	5,825
Regulatory assets	105,253	107,166
Pension benefits	16,013	15,071
Other deferred assets and other	4,818	6,138
Property, Plant, and Equipment:
Property, plant, and equipment, net	1,025,886	1,017,877
Construction work in progress	147,449	141,415
Total Property, Plant, and Equipment	1,173,335	1,159,292
Investments	66,426	65,299
Total Assets	1,555,393	1,530,643
Current Liabilities:
Long-term debt due within one year	4,121	4,102
Accounts payable	56,171	43,684
Accrued interest and taxes	10,019	6,040
Accrued payroll related items	8,103	10,731
Deferred income taxes	707	2,723
Regulatory liabilities - current	11,537	13,538
Derivative liabilities	6,540	7,750
Other current liabilities	8,244	6,446
Total Current Liabilities	105,442	95,014
Other Credits:
Deferred income taxes	281,261	279,085
Investment tax credit - deferred	1,362	1,413
Regulatory liabilities	20,788	19,792
Accrued pension and other postretirement benefits	49,512	49,184
Derivative liabilities	53,750	57,930
Other deferred liabilities and other	54,156	52,357
Total Other Credits	460,829	459,761
Capitalization:
Common shareholders equity	471,642	457,491
Noncontrolling interest	119,097	118,963
Total Equity	590,739	576,454
Long-term debt	398,383	399,414
Total Capitalization	989,122	975,868
Commitments and contingencies (see Footnote 8)
Total Liabilities and Capitalization	$ 1,555,393	$ 1,530,643