Consolidated Balance Sheets - USD ($)		Dec. 31, 2019	Dec. 31, 2018
Current Assets:
Cash and cash equivalents		$ 23,481,000	$ 83,102,000
Accounts receivable, less reserves		40,482,000	43,593,000
Other accounts receivables, less reserves		7,940,000	6,262,000
Unbilled revenues		25,899,000	28,243,000
Materials and supplies, at average cost		26,287,000	24,093,000
Fuel for electric generation, at average cost		8,358,000	6,599,000
Stored natural gas, at average cost		10,637,000	11,303,000
Prepaid taxes		16,892,000	16,215,000
Regulatory assets - current		11,432,000	9,477,000
Assets held for sale		0	3,080,000
Other current assets		10,233,000	8,593,000
Total Current Assets		181,641,000	240,560,000
Other long-term receivables		1,811,000	2,709,000
Regulatory assets		134,314,000	145,424,000
Pension and other postretirement benefit asset		13,630,000	0
Other deferred assets and other		19,093,000	12,488,000
Property, Plant, and Equipment:
Property, plant, and equipment, net		1,530,199,000	1,369,766,000
Construction work in progress		112,484,000	139,671,000
Total Property, Plant, and Equipment		1,642,683,000	1,509,437,000
Investments		88,492,000	78,000,000
Total Assets		2,081,664,000	1,988,618,000
Current Liabilities:
Long-term debt due within one year		19,659,000	4,553,000
Short-term debt	[1]	0	13,000,000
Accounts payable		55,161,000	46,158,000
Accrued interest and taxes		7,244,000	7,384,000
Accrued payroll related items		12,752,000	13,044,000
Regulatory liabilities - current		9,228,000	13,826,000
Derivative liabilities		10,100,000	8,550,000
Other current liabilities		14,676,000	14,113,000
Total Current Liabilities		128,820,000	120,628,000
Other Credits:
Deferred income taxes		243,302,000	231,952,000
Investment tax credit - deferred		763,000	818,000
Regulatory liabilities		164,965,000	165,638,000
Accrued pension and other postretirement benefits		68,665,000	67,483,000
Derivative liabilities		15,340,000	23,980,000
Finance lease liabilities		17,379,000	1,771,000
Other deferred liabilities and other		63,013,000	66,361,000
Total Other Credits		573,427,000	558,003,000
Common shareholders' equity:
Common stock		34,668,000	34,668,000
Additional paid-in capital		316,268,000	316,268,000
Retained earnings		504,740,000	465,708,000
Total Common Shareholders' Equity		855,676,000	816,644,000
Long-term debt		523,741,000	493,343,000
Total Capitalization		1,379,417,000	1,309,987,000
Commitments and contingencies (see Footnote 16)
Total Liabilities and Capitalization		2,081,664,000	1,988,618,000
MGE [Member]
Current Assets:
Cash and cash equivalents		3,196,000	4,843,000
Accounts receivable, less reserves		40,482,000	43,593,000
Affiliate receivables		530,000	621,000
Other accounts receivables, less reserves		7,936,000	6,111,000
Unbilled revenues		25,899,000	28,243,000
Materials and supplies, at average cost		26,287,000	24,093,000
Fuel for electric generation, at average cost		8,358,000	6,599,000
Stored natural gas, at average cost		10,637,000	11,303,000
Prepaid taxes		15,463,000	15,790,000
Regulatory assets - current		11,432,000	9,477,000
Assets held for sale		0	3,080,000
Other current assets		10,065,000	8,541,000
Total Current Assets		160,285,000	162,294,000
Affiliate receivable long-term		2,648,000	3,177,000
Regulatory assets		134,314,000	145,424,000
Pension and other postretirement benefit asset		13,630,000	0
Other deferred assets and other		19,680,000	14,142,000
Property, Plant, and Equipment:
Property, plant, and equipment, net		1,530,227,000	1,369,795,000
Construction work in progress		112,484,000	139,671,000
Total Property, Plant, and Equipment		1,642,711,000	1,509,466,000
Investments		209,000	388,000
Total Assets		1,973,477,000	1,834,891,000
Current Liabilities:
Long-term debt due within one year		19,659,000	4,553,000
Short-term debt		0	13,000,000
Accounts payable		54,845,000	46,165,000
Accrued interest and taxes		8,754,000	10,319,000
Accrued payroll related items		12,752,000	13,044,000
Regulatory liabilities - current		9,228,000	13,826,000
Derivative liabilities		10,100,000	8,550,000
Other current liabilities		12,683,000	11,614,000
Total Current Liabilities		128,021,000	121,071,000
Other Credits:
Deferred income taxes		214,041,000	204,616,000
Investment tax credit - deferred		763,000	818,000
Regulatory liabilities		164,965,000	165,638,000
Accrued pension and other postretirement benefits		68,665,000	67,483,000
Derivative liabilities		15,340,000	23,980,000
Finance lease liabilities		17,379,000	1,771,000
Other deferred liabilities and other		62,973,000	66,361,000
Total Other Credits		544,126,000	530,667,000
Common shareholders' equity:
Common stock		17,348,000	17,348,000
Additional paid-in capital		222,917,000	192,417,000
Retained earnings		397,021,000	338,591,000
Total Common Shareholders' Equity		637,286,000	548,356,000
Noncontrolling interest		140,303,000	141,454,000
Total Equity		777,589,000	689,810,000
Long-term debt		523,741,000	493,343,000
Total Capitalization		1,301,330,000	1,183,153,000
Commitments and contingencies (see Footnote 16)
Total Liabilities and Capitalization		$ 1,973,477,000	$ 1,834,891,000

[1] (a) MGE Energy short-term borrowings include MGE Energy and MGE lines of credit and MGE commercial paper.