Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current Assets:
Cash and cash equivalents	$ 101,157	$ 107,952
Accounts receivable, less reserves	43,307	42,299
Other accounts receivables, less reserves	5,851	9,440
Unbilled revenues	25,471	31,400
Materials and supplies, at average cost	23,554	22,614
Fuel for electric generation, at average cost	9,478	8,256
Stored natural gas, at average cost	3,686	12,923
Prepaid taxes	14,956	26,535
Regulatory assets - current	8,721	7,888
Assets held for sale	1,383	8,817
Other current assets	11,176	12,507
Total Current Assets	248,740	290,631
Other long-term receivables	4,449	4,788
Regulatory assets	140,218	142,567
Pension and other postretirement benefit asset	9,631	7,336
Other deferred assets and other	2,150	731
Property, Plant, and Equipment:
Property, plant, and equipment, net	1,290,148	1,283,313
Construction work in progress	76,066	58,044
Total Property, Plant, and Equipment	1,366,214	1,341,357
Investments	72,176	67,772
Total Assets	1,843,578	1,855,182
Current Liabilities:
Long-term debt due within one year	24,477	24,452
Short-term debt	3,000	4,000
Accounts payable	35,026	47,645
Accrued interest and taxes	4,497	5,602
Accrued payroll related items	8,390	12,244
Regulatory liabilities - current	12,325	5,633
Derivative liabilities	8,950	8,180
Other current liabilities	9,565	18,758
Total Current Liabilities	106,230	126,514
Other Credits:
Deferred income taxes	224,309	225,130
Investment tax credit - deferred	893	918
Regulatory liabilities	157,890	154,153
Accrued pension and other postretirement benefits	69,030	69,088
Derivative liabilities	32,340	33,990
Other deferred liabilities and other	68,746	69,041
Total Other Credits	553,208	552,320
Capitalization:
Common shareholders equity	787,007	778,187
Long-term debt	397,133	398,161
Total Capitalization	1,184,140	1,176,348
Commitments and contingencies (see Footnote 9)
Total Liabilities and Capitalization	1,843,578	1,855,182
MGE [Member]
Current Assets:
Cash and cash equivalents	4,152	5,951
Accounts receivable, less reserves	43,307	42,299
Affiliate receivables	690	668
Other accounts receivables, less reserves	5,740	6,984
Unbilled revenues	25,471	31,400
Materials and supplies, at average cost	23,554	22,614
Fuel for electric generation, at average cost	9,478	8,256
Stored natural gas, at average cost	3,686	12,923
Prepaid taxes	13,893	25,073
Regulatory assets - current	8,721	7,888
Assets held for sale	1,383	8,817
Other current assets	11,162	12,484
Total Current Assets	151,237	185,357
Affiliate receivable long-term	3,574	3,707
Regulatory assets	140,218	142,567
Pension and other postretirement benefit asset	9,631	7,336
Other deferred assets and other	4,512	3,280
Property, Plant, and Equipment:
Property, plant, and equipment, net	1,290,176	1,283,341
Construction work in progress	76,066	58,044
Total Property, Plant, and Equipment	1,366,242	1,341,385
Investments	409	409
Total Assets	1,675,823	1,684,041
Current Liabilities:
Long-term debt due within one year	24,477	24,452
Short-term debt	3,000	4,000
Accounts payable	35,026	47,614
Accrued interest and taxes	4,443	5,558
Accrued payroll related items	8,390	12,244
Regulatory liabilities - current	12,325	5,633
Derivative liabilities	8,950	8,180
Other current liabilities	9,557	16,749
Total Current Liabilities	106,168	124,430
Other Credits:
Deferred income taxes	200,093	201,486
Investment tax credit - deferred	893	918
Regulatory liabilities	157,890	154,153
Accrued pension and other postretirement benefits	69,030	69,088
Derivative liabilities	32,340	33,990
Other deferred liabilities and other	68,746	69,041
Total Other Credits	528,992	528,676
Capitalization:
Common shareholders equity	504,322	491,872
Noncontrolling interest	139,208	140,902
Total Equity	643,530	632,774
Long-term debt	397,133	398,161
Total Capitalization	1,040,663	1,030,935
Commitments and contingencies (see Footnote 9)
Total Liabilities and Capitalization	$ 1,675,823	$ 1,684,041