Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current Assets:
Cash and cash equivalents	$ 70,703	$ 65,755
Accounts receivable, less reserves	43,861	41,614
Other accounts receivables, less reserves	6,443	7,610
Unbilled revenues	25,366	31,262
Materials and supplies, at average cost	18,027	17,121
Fossil fuel	14,418	8,098
Stored natural gas, at average cost	8,398	21,036
Prepaid taxes	30,860	38,910
Regulatory assets - current	7,537	8,360
Deferred income taxes - current	109	3,482
Other current assets	10,219	10,711
Total Current Assets	235,941	253,959
Other long-term receivables	5,454	2,181
Regulatory assets	155,473	156,823
Other deferred assets and other	4,548	4,837
Property, Plant, and Equipment:
Property, plant, and equipment, net	1,189,106	1,189,077
Construction work in progress	21,322	19,029
Total Property, Plant, and Equipment	1,210,428	1,208,106
Investments	72,347	71,760
Total Assets	1,684,191	1,697,666
Current Liabilities:
Long-term debt due within one year	4,203	4,182
Short-term debt	0	7,000
Accounts payable	37,540	41,655
Accrued interest and taxes	3,999	5,086
Accrued payroll related items	8,318	11,241
Derivative liabilities	7,120	6,901
Other current liabilities	10,511	13,931
Total Current Liabilities	71,691	89,996
Other Credits:
Deferred income taxes	342,400	342,045
Investment tax credit - deferred	1,179	1,223
Regulatory liabilities	23,981	22,715
Accrued pension and other postretirement benefits	79,742	90,201
Derivative liabilities	46,319	46,560
Other deferred liabilities and other	57,017	50,269
Total Other Credits	550,638	553,013
Capitalization:
Common shareholders equity	667,658	659,401
Long-term debt	394,204	395,256
Total Capitalization	1,061,862	1,054,657
Commitments and contingencies (see Footnote 8)
Total Liabilities and Capitalization	1,684,191	1,697,666
MGE [Member]
Current Assets:
Cash and cash equivalents	17,156	4,562
Accounts receivable, less reserves	43,861	41,614
Affiliate receivables	568	7,112
Other accounts receivables, less reserves	6,346	7,524
Unbilled revenues	25,366	31,262
Materials and supplies, at average cost	18,027	17,121
Fossil fuel	14,418	8,098
Stored natural gas, at average cost	8,398	21,035
Prepaid taxes	36,755	39,103
Regulatory assets - current	7,537	8,360
Deferred income taxes - current	0	1,271
Other current assets	10,203	10,683
Total Current Assets	188,635	197,745
Affiliate receivable long-term	5,163	5,295
Regulatory assets	155,473	156,823
Other deferred assets and other	7,953	4,977
Property, Plant, and Equipment:
Property, plant, and equipment, net	1,188,392	1,188,351
Construction work in progress	21,322	19,029
Total Property, Plant, and Equipment	1,209,714	1,207,380
Investments	68,904	68,402
Total Assets	1,635,842	1,640,622
Current Liabilities:
Long-term debt due within one year	4,203	4,182
Short-term debt	0	7,000
Accounts payable	37,540	41,654
Accrued interest and taxes	3,954	5,039
Accrued payroll related items	8,318	11,241
Deferred income taxes	898	0
Derivative liabilities	7,120	6,901
Other current liabilities	10,159	11,350
Total Current Liabilities	72,192	87,367
Other Credits:
Deferred income taxes	335,002	334,773
Investment tax credit - deferred	1,179	1,223
Regulatory liabilities	23,981	22,715
Accrued pension and other postretirement benefits	79,742	90,201
Derivative liabilities	46,319	46,560
Other deferred liabilities and other	57,016	50,267
Total Other Credits	543,239	545,739
Capitalization:
Common shareholders equity	498,105	486,571
Noncontrolling interest	128,102	125,689
Total Equity	626,207	612,260
Long-term debt	394,204	395,256
Total Capitalization	1,020,411	1,007,516
Commitments and contingencies (see Footnote 8)
Total Liabilities and Capitalization	$ 1,635,842	$ 1,640,622