Consolidated Balance Sheets (Unaudited) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Current Assets:
Cash and cash equivalents	$ 40,239,000	$ 44,738,000
Accounts receivable, less reserves	43,172,000	41,384,000
Other accounts receivables, less reserves	9,702,000	7,300,000
Unbilled revenues	25,148,000	27,511,000
Materials and supplies, at average cost	32,222,000	32,513,000
Fuel for electric generation, at average cost	4,885,000	6,356,000
Stored natural gas, at average cost	1,578,000	8,396,000
Prepaid taxes	11,210,000	15,179,000
Regulatory assets - current	24,313,000	14,748,000
Other current assets	9,042,000	11,394,000
Total Current Assets	201,511,000	209,519,000
Other long-term receivables	1,486,000	1,435,000
Regulatory assets	139,667,000	142,504,000
Pension benefit asset	17,848,000	13,873,000
Other deferred assets and other	22,564,000	22,259,000
Property, Plant, and Equipment:
Property, plant, and equipment, net	1,633,908,000	1,630,286,000
Construction work in progress	157,970,000	139,099,000
Total Property, Plant, and Equipment	1,791,878,000	1,769,385,000
Investments	95,283,000	94,676,000
Total Assets	2,270,237,000	2,253,651,000
Current Liabilities:
Long-term debt due within one year	4,800,000	4,771,000
Short-term debt	54,000,000	52,500,000
Accounts payable	53,840,000	54,642,000
Accrued interest and taxes	7,540,000	8,539,000
Accrued payroll related items	10,019,000	12,635,000
Regulatory liabilities - current	37,035,000	41,664,000
Derivative liabilities	9,790,000	10,160,000
Other current liabilities	6,774,000	6,015,000
Total Current Liabilities	183,798,000	190,926,000
Other Credits:
Deferred income taxes	236,903,000	231,471,000
Investment tax credit - deferred	21,588,000	21,821,000
Regulatory liabilities	143,365,000	142,239,000
Accrued pension and other postretirement benefits	77,941,000	78,168,000
Derivative liabilities	1,800,000	3,980,000
Finance lease liabilities	17,623,000	17,532,000
Other deferred liabilities and other	71,297,000	72,211,000
Total Other Credits	570,517,000	567,422,000
Capitalization:
Common shareholders equity	997,711,000	976,000,000
Long-term debt	518,211,000	519,303,000
Total Capitalization	1,515,922,000	1,495,303,000
Commitments and contingencies (see Footnote 8)
Total Liabilities and Capitalization	2,270,237,000	2,253,651,000
MGE [Member]
Current Assets:
Cash and cash equivalents	6,709,000	4,103,000
Accounts receivable, less reserves	43,172,000	41,384,000
Affiliate receivables	530,000	532,000
Other accounts receivables, less reserves	9,698,000	7,295,000
Unbilled revenues	25,148,000	27,511,000
Materials and supplies, at average cost	32,222,000	32,513,000
Fuel for electric generation, at average cost	4,885,000	6,356,000
Stored natural gas, at average cost	1,578,000	8,396,000
Prepaid taxes	11,102,000	14,848,000
Regulatory assets - current	24,313,000	14,748,000
Other current assets	8,940,000	11,326,000
Total Current Assets	168,297,000	169,012,000
Affiliate receivable long-term	1,986,000	2,118,000
Regulatory assets	139,667,000	142,504,000
Pension benefit asset	17,848,000	13,873,000
Other deferred assets and other	22,877,000	22,448,000
Property, Plant, and Equipment:
Property, plant, and equipment, net	1,633,936,000	1,630,314,000
Construction work in progress	157,970,000	139,099,000
Total Property, Plant, and Equipment	1,791,906,000	1,769,413,000
Investments	433,000	603,000
Total Assets	2,143,014,000	2,119,971,000
Current Liabilities:
Long-term debt due within one year	4,800,000	4,771,000
Short-term debt	54,000,000	52,500,000
Accounts payable	53,808,000	54,576,000
Accrued interest and taxes	9,574,000	10,405,000
Accrued payroll related items	10,019,000	12,635,000
Regulatory liabilities - current	37,035,000	41,664,000
Derivative liabilities	9,790,000	10,160,000
Other current liabilities	6,776,000	6,042,000
Total Current Liabilities	185,802,000	192,753,000
Other Credits:
Deferred income taxes	204,853,000	200,390,000
Investment tax credit - deferred	21,588,000	21,821,000
Regulatory liabilities	143,365,000	142,239,000
Accrued pension and other postretirement benefits	77,941,000	78,168,000
Derivative liabilities	1,800,000	3,980,000
Finance lease liabilities	17,623,000	17,532,000
Other deferred liabilities and other	71,445,000	72,173,000
Total Other Credits	538,615,000	536,303,000
Capitalization:
Common shareholders equity	758,689,000	730,416,000
Noncontrolling interest	141,697,000	141,196,000
Total Equity	900,386,000	871,612,000
Long-term debt	518,211,000	519,303,000
Total Capitalization	1,418,597,000	1,390,915,000
Commitments and contingencies (see Footnote 8)
Total Liabilities and Capitalization	$ 2,143,014,000	$ 2,119,971,000