Madison Gas & Electric 10-Q 6 May 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	Apr. 30, 2021
Document And Entity Information [Line Items]
Entity Registrant Name	MGE Energy, Inc.
Entity Central Index Key	0001161728
Document Type	10-Q
Document Period End Date	Mar. 31, 2021
Amendment Flag	false
Trading Symbol	MGEE
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock Shares Outstanding		36,163,370
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Security Exchange Name	NASDAQ
Security 12(b) Title	Common Stock, $1 Par Value Per Share
Entity Tax Identification Number	39-2040501
Entity File Number	000-49965
Entity Incorporation State Country Code	WI
Entity Address Address Line 1	133 South Blair Street
EntityAddressCityOrTown	Madison
Entity Address State Or Province	WI
Entity Address Postal Zip Code	53788
City Area Code	608
Local Phone Number	252-7000
Document Transition Report	false
Entity Interactive Data Current	Yes
Document Quarterly Report	true
MGE [Member]
Document And Entity Information [Line Items]
Entity Registrant Name	Madison Gas and Electric Company
Entity Central Index Key	0000061339
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock Shares Outstanding		17,347,894
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Tax Identification Number	39-0444025
Entity File Number	000-1125
Entity Incorporation State Country Code	WI
Entity Address Address Line 1	133 South Blair Street
EntityAddressCityOrTown	Madison
Entity Address State Or Province	WI
Entity Address Postal Zip Code	53788
City Area Code	608
Local Phone Number	252-7000
Document Transition Report	false
Entity Interactive Data Current	Yes
Document Quarterly Report	true

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating Revenues:
Electric revenues	$ 100,645	$ 93,028
Gas revenue	67,270	56,845
Total Operating Revenues	167,915	149,873
Operating Expenses:
Fuel for electric generation	13,171	9,706
Purchased power	9,355	10,486
Cost of gas sold	37,444	30,798
Other operations and maintenance	45,682	44,369
Depreciation and amortization	18,382	18,167
Other general taxes	4,827	4,907
Total Operating Expenses	128,861	118,433
Operating Income	39,054	31,440
Other (expense) income, net	2,078	5,671
Interest expense, net	(5,740)	(6,061)
Income before income taxes	35,392	31,050
Income tax benefit (provision)	(459)	(5,013)
Net Income Including Noncontrolling Interest	34,933	26,037
Net Income	$ 34,933	$ 26,037
Earnings per share of Common Stock - Basic	$ 0.97	$ 0.75
Earnings per share of Common Stock - Diluted	0.97	0.75
Dividends per share of common stock	$ 0.370	$ 0.353
Weighted Average Number Of Shares Outstanding Basic	36,163	34,668
Weighted Average Shares Outstanding - Diluted	36,165	34,668
MGE [Member]
Operating Revenues:
Electric revenues	$ 100,645	$ 93,028
Gas revenue	67,270	56,845
Total Operating Revenues	167,915	149,873
Operating Expenses:
Fuel for electric generation	13,171	9,706
Purchased power	9,355	10,486
Cost of gas sold	37,444	30,798
Other operations and maintenance	45,538	44,150
Depreciation and amortization	18,382	18,167
Other general taxes	4,827	4,907
Total Operating Expenses	128,717	118,214
Operating Income	39,198	31,659
Other (expense) income, net	(104)	3,380
Interest expense, net	(5,753)	(6,111)
Income before income taxes	33,341	28,928
Income tax benefit (provision)	433	(4,371)
Net Income Including Noncontrolling Interest	33,774	24,557
Less Net Income Attributable to Noncontrolling Interest, net of tax	(5,501)	(5,493)
Net Income	$ 28,273	$ 19,064

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating Activities:
Net Income	$ 34,933,000	$ 26,037,000
Items not affecting cash:
Depreciation and amortization	18,382,000	18,167,000
Deferred income taxes	(796,000)	1,433,000
Provision for doubtful receivables	388,000	734,000
Employee benefit plan cost (credit)	1,461,000	(940,000)
Equity earnings in investments	(2,444,000)	(2,266,000)
Other items	(277,000)	(1,974,000)
Changes in working capital items:
(Increase) decrease in current assets	(2,851,000)	14,089,000
(Decrease) increase in current liabilities	(4,213,000)	(2,738,000)
Dividends from investments	1,967,000	2,700,000
Cash contributions to pension and other postretirement plans	(1,552,000)	(1,470,000)
Other noncurrent items, net	(1,115,000)	47,000
Cash Provided by Operating Activities	43,883,000	53,819,000
Investing Activities:
Capital expenditures	(34,746,000)	(46,758,000)
Capital contributions to investments	(670,000)	(1,643,000)
Other	(419,000)	(398,000)
Cash Used for Investing Activities	(35,835,000)	(48,799,000)
Financing Activities:
Cash dividends paid on common stock	(13,380,000)	(12,221,000)
Repayments of long-term debt	(1,182,000)	(1,155,000)
Net proceeds from short-term debt	1,500,000	3,000,000
Other	(523,000)	(664,000)
Cash Used for Financing Activities	(13,585,000)	(11,040,000)
Change in cash, cash equivalents, and restricted cash	(5,537,000)	(6,020,000)
Cash, cash equivalents, and restricted cash at beginning of period	47,039,000	25,814,000
Cash, cash equivalents, and restricted cash at end of period	41,502,000	19,794,000
Significant noncash investing activities:
Accrued capital expenditures	8,843,000	8,129,000
MGE [Member]
Operating Activities:
Net Income	33,774,000	24,557,000
Items not affecting cash:
Depreciation and amortization	18,382,000	18,167,000
Deferred income taxes	(1,766,000)	976,000
Provision for doubtful receivables	388,000	734,000
Employee benefit plan cost (credit)	1,461,000	(940,000)
Other items	(252,000)	(1,721,000)
Changes in working capital items:
(Increase) decrease in current assets	(3,037,000)	12,953,000
(Decrease) increase in current liabilities	(4,037,000)	290,000
Cash contributions to pension and other postretirement plans	(1,552,000)	(1,470,000)
Other noncurrent items, net	(1,380,000)	(428,000)
Cash Provided by Operating Activities	41,981,000	53,118,000
Investing Activities:
Capital expenditures	(34,746,000)	(46,758,000)
Other	(462,000)	(406,000)
Cash Used for Investing Activities	(35,208,000)	(47,164,000)
Financing Activities:
Distributions to parent from noncontrolling interest	(5,000,000)	(7,000,000)
Repayments of long-term debt	(1,182,000)	(1,155,000)
Net proceeds from short-term debt	1,500,000	3,000,000
Other	(523,000)	(664,000)
Cash Used for Financing Activities	(5,205,000)	(5,819,000)
Change in cash, cash equivalents, and restricted cash	1,568,000	135,000
Cash, cash equivalents, and restricted cash at beginning of period	6,404,000	5,529,000
Cash, cash equivalents, and restricted cash at end of period	7,972,000	5,664,000
Significant noncash investing activities:
Accrued capital expenditures	$ 8,843,000	$ 8,129,000

Consolidated Balance Sheets (Un

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

Consolidated Balance Sheets (_2

Consolidated Balance Sheets (Unaudited) (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Receivables, Net
Reserve for uncollectible accounts receivable	$ 6,382	$ 5,787
Reserve for uncollectible other accounts receivable	1,307	1,290
MGE [Member]
Receivables, Net
Reserve for uncollectible accounts receivable	6,382	5,787
Reserve for uncollectible other accounts receivable	$ 1,307	$ 1,290

MGE Energy Inc Consolidated Sta

MGE Energy Inc Consolidated Statements of Common Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]
Beginning balance, shares at Dec. 31, 2019		34,668
Beginning balance, value at Dec. 31, 2019	$ 855,676	$ 34,668	$ 316,268	$ 504,740	$ 0
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income	26,037			26,037
Common stock dividends declared	(12,221)			(12,221)
Ending balance, shares at Mar. 31, 2020		34,668
Ending balance, value at Mar. 31, 2020	869,492	$ 34,668	316,268	518,556	0
Beginning balance, shares at Dec. 31, 2020		36,163
Beginning balance, value at Dec. 31, 2020	976,000	$ 36,163	394,408	545,429	0
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income	34,933			34,933
Common stock dividends declared	(13,380)			(13,380)
Equity-based compensation plans and other	158		158
Ending balance, shares at Mar. 31, 2021		36,163
Ending balance, value at Mar. 31, 2021	$ 997,711	$ 36,163	$ 394,566	$ 566,982	$ 0

Madison Gas and Electric Compan

Madison Gas and Electric Company Consolidated Statements of Common Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	MGE [Member]	Common Stock [Member]	Common Stock [Member]MGE [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member]MGE [Member]	Retained Earnings [Member]MGE [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]MGE [Member]	Noncontrolling Interest [Member]MGE [Member]
Beginning balance, shares at Dec. 31, 2019			34,668	17,348
Beginning balance, value at Dec. 31, 2019		$ 777,589		$ 17,348		$ 222,917	$ 397,021	$ 0	$ 140,303
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income	$ 26,037	24,557					19,064		5,493
Distributions to parent from noncontrolling interest		(7,000)							(7,000)
Ending balance, shares at Mar. 31, 2020			34,668	17,348
Ending balance, value at Mar. 31, 2020		795,146		$ 17,348		222,917	416,085	0	138,796
Beginning balance, shares at Dec. 31, 2020			36,163	17,348
Beginning balance, value at Dec. 31, 2020		871,612		$ 17,348		252,917	460,151	0	141,196
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income	34,933	33,774					28,273		5,501
Distributions to parent from noncontrolling interest		(5,000)							(5,000)
Equity-based compensation plans and other	$ 158				$ 158
Ending balance, shares at Mar. 31, 2021			36,163	17,348
Ending balance, value at Mar. 31, 2021		$ 900,386		$ 17,348		$ 252,917	$ 488,424	$ 0	$ 141,697

Consolidated Statements of Comm

Consolidated Statements of Common Equity (Unaudited) (Parentheticals) - $ / shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Consolidated Statements of Common Equity
Dividends per share of common stock	$ 0.370	$ 0.353

Summary of Significant Accounti

Summary of Significant Accounting Principles	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies – MGE Energy and MGE. a. Basis of Presentation. This report is a combined report of MGE Energy and MGE. References in this report to "MGE Energy" are to MGE Energy, Inc. and its subsidiaries. References in this report to "MGE" are to Madison Gas and Electric Company. MGE Power Elm Road and MGE Power West Campus own electric generating assets and lease those assets to MGE. Both entities are variable interest entities under applicable authoritative accounting guidance. MGE is considered the primary beneficiary of these entities as a result of contractual agreements. As a result, MGE has consolidated MGE Power Elm Road and MGE Power West Campus. See Footnote 3 of Notes to Consolidated Financial Statements under Item 8, Financial Statements and Supplementary Data, of MGE Energy's and MGE's 2020 Annual Report on Form 10-K (the 2020 Annual Report on Form 10-K). The accompanying consolidated financial statements as of March 31, 2021, and during the three months ended, are unaudited but include all adjustments that MGE Energy and MGE management consider necessary for a fair statement of their respective financial statements. All adjustments are of a normal, recurring nature except as otherwise disclosed. The year-end consolidated balance sheet information was derived from the audited balance sheet appearing in the 2020 Annual Report on Form 10-K but does not include all disclosures required by accounting principles generally accepted in the United States of America. These notes should be read in conjunction with the financial statements and the notes on pages 62 through 115 of the 2020 Annual Report on Form 10-K. b. Cash, Cash Equivalents, and Restricted Cash. The following table presents the components of total cash, cash equivalents, and restricted cash on the consolidated balance sheets. MGE Energy MGE March 31, December 31, March 31, December 31, (In thousands) 2021 2020 2021 2020 Cash and cash equivalents $ 40,239 $ 44,738 $ 6,709 $ 4,103 Restricted cash 467 644 467 644 Receivable - margin account 796 1,657 796 1,657 Cash, cash equivalents, and restricted cash $ 41,502 $ 47,039 $ 7,972 $ 6,404 Cash Equivalents All highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. Restricted Cash MGE has certain cash accounts that are restricted to uses other than current operations and designated for a specific purpose. MGE's restricted cash accounts include cash held by trustees for certain employee benefits and cash deposits held by third parties. These are included in "Other current assets" on the consolidated balance sheets. Receivable – Margin Account Cash amounts held by counterparties as margin collateral for certain financial transactions are recorded as Receivable – margin account in "Other current assets" on the consolidated balance sheets. The costs being hedged are fuel for electric generation, purchased power, and cost of gas sold.

Adoption of Accounting Principl

Adoption of Accounting Principles and Recently Issued Accounting Pronouncements	3 Months Ended
	Mar. 31, 2021
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New Accounting Pronouncements	New Accounting Standards - MGE Energy and MGE. MGE Energy and MGE reviewed FASB authoritative guidance recently issued, none of which are expected to have a material impact on the consolidated results of operations, financial condition, or cash flows.

Investment in ATC and ATC Holdc

Investment in ATC and ATC Holdco	3 Months Ended
	Mar. 31, 2021
Equity Method Investments and Joint Ventures [Abstract]
Investment in ATC and ATC Holdco	Investment in ATC and ATC Holdco - MGE Energy and MGE. ATC owns and operates electric transmission facilities primarily in Wisconsin. MGE received an interest in ATC when it, like other Wisconsin electric utilities, contributed its electric transmission facilities to ATC as required by Wisconsin law. That interest is presently held by MGE Transco, a subsidiary of MGE Energy. ATC Holdco was formed by several members of ATC, including MGE Energy, to pursue electric transmission development and investments outside of Wisconsin. The ownership interest in ATC Holdco is held by MGEE Transco, a subsidiary of MGE Energy. MGE Transco and MGEE Transco have accounted for their investments in ATC and ATC Holdco, respectively, under the equity method of accounting. Equity earnings from investments are recorded as "Other income" on the consolidated statements of income of MGE Energy. MGE Transco recorded the following amounts related to its investment in ATC: Three Months Ended March 31, (In thousands) 2021 2020 Equity earnings from investment in ATC $ 2,420 $ 2,266 Dividends from ATC 1,967 2,391 Capital contributions to ATC - 178 ATC Holdco was formed in December 2016. ATC Holdco's future transmission development activities have been suspended for the near term. ATC ' s summarized financial data is as follows: Three Months Ended March 31, (In thousands) 2021 2020 Operating revenues $ 188,694 $ 186,801 Operating expenses ( 95,104) ( 95,211) Other income, net 378 375 Interest expense, net ( 28,871) ( 28,888) Earnings before members' income taxes $ 65,097 $ 63,077 MGE receives transmission and other related services from ATC. During the three months ended March 31, 2021 and 2020, MGE recorded $ 8.0 million and $ 7.7 million, respectively, for transmission services received from ATC. MGE also provides a variety of operational, maintenance, and project management work for ATC, which is reimbursed by ATC. As of March 31, 2021, and December 31, 2020, MGE had a receivable due from ATC of $ 3.0 and $ 2.6 million, respectively. The receivable is primarily related to Badger Hollow I and II. MGE is reimbursed for these costs after the new generation assets are placed into service.

Taxes

Taxes	3 Months Ended
	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Taxes	Taxes - MGE Energy and MGE. Effective Tax Rate. The consolidated income tax provision differs from the amount computed by applying the statutory federal income tax rate to income before income taxes, as follows: MGE Energy MGE Three Months Ended March 31, 2021 2020 2021 2020 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefit 6.3 6.3 6.3 6.3 Amortized investment tax credits ( 1.6) ( 0.1) ( 1.8) ( 0.1) Credit for electricity from wind energy ( 7.1) ( 6.9) ( 7.8) ( 7.5) AFUDC equity, net ( 0.6) ( 1.6) ( 0.6) ( 1.7) Amortization of utility excess deferred tax - tax reform (a) ( 16.7) ( 2.6) ( 18.3) ( 2.8) Other, net, individually insignificant - - ( 0.1) ( 0.1) Effective income tax rate 1.3 % 16.1 % ( 1.3) % 15.1 % (a) Included are impacts of the 2017 Tax Act for the regulated utility for excess deferred taxes recognized using a normalization method of accounting in recognition of IRS rules that restrict the rate at which the excess deferred taxes may be returned to utility customers. For the three months ended March 31, 2021 and 2020, MGE recognized $ 0.7 million. Included in the 2021 rate settlement was a one-time return to customers of the electric portion of excess deferred taxes related to the 2017 Tax Act not restricted by IRS normalization rules. For the three months ended March 31, 2021, MGE recognized $ 3.3 million.

Pension and Other Postretiremen

Pension and Other Postretirement Plans	3 Months Ended
	Mar. 31, 2021
Compensation and Retirement Disclosure [Abstract]
Pension and Other Postretirement Plans	Pension and Other Postretirement Plans - MGE Energy and MGE. MGE maintains qualified and nonqualified pension plans, health care, and life insurance benefits and defined contribution 401(k) benefit plans for its employees and retirees. The components of net periodic benefit cost, other than the service cost component, are recorded in " Other income, net " on the consolidated statements of income. The service cost component is recorded in " Other operations and maintenance " on the consolidated statements of income. MGE has regulatory treatment and recognizes regulatory assets or liabilities for timing differences between when net periodic benefit costs are recovered and when costs are recognized. The following table presents the components of net periodic benefit costs recognized. Three Months Ended March 31, (In thousands) 2021 2020 Pension Benefits Components of net periodic benefit cost: Service cost $ 1,422 $ 1,316 Interest cost 2,272 3,023 Expected return on assets ( 7,375) ( 6,811) Amortization of: Prior service credit ( 31) ( 31) Actuarial loss 1,580 1,286 Net periodic benefit (credit) cost $ ( 2,132) $ ( 1,217) Postretirement Benefits Components of net periodic benefit cost: Service cost $ 351 $ 311 Interest cost 384 573 Expected return on assets ( 817) ( 790) Amortization of: Transition obligation 1 1 Prior service credit ( 380) ( 667) Actuarial loss 109 70 Net periodic benefit (credit) cost $ ( 352) $ ( 502) As approved by the PSCW, MGE is allowed to defer differences between actual employee benefit plan costs and costs reflected in current rates. The deferred costs may be recovered or refunded in MGE's next rate filing. For the three months ended March 31, 2021 and 2020, MGE recovered approximately $ 3.4 million and $ 0.4 million, respectively, of pension and other postretirement costs, which reduced the amount previously deferred and has not been reflected in the table above.

Equity and Financing Arrangemen

Equity and Financing Arrangements	3 Months Ended
	Mar. 31, 2021
Equity and Financing Arrangements Disclosure [Abstract]
Equity and Financing Arrangements	Equity and Financing Arrangements. a. Common Stock - MGE Energy. MGE Energy sells shares of its common stock through its Direct Stock Purchase and Dividend Reinvestment Plan (the Stock Plan). Those shares may be newly issued shares or shares that are purchased in the open market by an independent agent for participants in the Stock Plan. All sales under the Stock Plan are covered by a shelf registration statement that MGE Energy filed with the SEC. During the three months ended March 31, 2021 and 2020, MGE Energy issued no new shares of common stock under the Stock Plan. b. Dilutive Shares Calculation - MGE Energy. As of March 31, 2021, 1,543 shares were included in the calculation of diluted earnings per share related to nonvested equity awards. See Footnote 7 for additional information on shared-based compensation awards.

Share-Based Compensation

Share-Based Compensation	3 Months Ended
	Mar. 31, 2021
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	Share-Based Compensation - MGE Energy and MGE. During the three months ended March 31, 2021 and 2020, MGE recorded $ 0.7 million in compensation expense and $ 0.6 million in compensation benefit, respectively, related to share-based compensation awards under the 2006 Performance Unit Plan, the 2020 Performance Unit Plan, the 2013 Director Incentive Plan, and the 2021 Long-Term Incentive Plan (2021 Plan). In January 2021, cash payments of $ 1.9 million were distributed related to awards that were granted under the plans in 2018, for the 2013 Director Incentive Plan, and in 2016, for the 2006 Performance Unit Plan. In February 2021, MGE issued 10,187 performance units and 16,267 restricted stock units under the 2021 Plan to eligible employees and non-employee directors. The performance units can be paid out in either cash, shares of common stock or a combination of cash and stock and are accounted for as a liability award. The restricted stock units will be paid out in shares of common stock, and therefore accounted for as equity awards.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies. a. Environmental - MGE Energy and MGE. In February 2021, MGE and the other co-owners of Columbia announced plans to retire that facility. The co-owners intend to retire Unit 1 by the end of 2023 and Unit 2 by the end of 2024. Final timing and retirement dates for Units 1 and 2 are subject to PSCW and regional regulatory reviews, including identification and approval of energy and capacity resources to replace Columbia. Effects of environmental compliance requirements discussed below will depend upon the final retirement dates approved and compliance requirement dates. MGE Energy and MGE are subject to frequently changing local, state, and federal regulations concerning air quality, water quality, land use, threatened and endangered species, hazardous materials handling, and solid waste disposal. These regulations affect the manner in which operations are conducted, the costs of operations, as well as capital and operating expenditures. Several of these environmental rules are subject to legal challenges, reconsideration and/or other uncertainties. Regulatory initiatives, proposed rules, and court challenges to adopted rules could have a material effect on capital expenditures and operating costs. Management believes compliance costs will be recovered in future rates based on previous treatment of environmental compliance projects. These initiatives, proposed rules, and court challenges include: • The EPA's promulgated water Effluent Limitations Guidelines (ELG) and standards for steam electric power plants which focus on the reduction of metals and other pollutants in wastewater from new and existing power plants. The standards were finalized in August 2020. In February 2021, MGE and the other owners of Columbia filed a Certificate of Authority (CA) application with the PSCW. The CA application commits to close Columbia's wet pond system to comply with the Coal Combustions Residuals (CCR) Rule as described in further detail in the CCR section below. By committing to close the wet pond system, Columbia will be in compliance with ELG requirements. The Elm Road Units must satisfy the rule's requirements no later than December 31, 2023, as determined by the permitting authority. The operator of the Elm Road Units has been evaluating the rule impacts and has conducted an analysis of compliance obligations, pollution prevention technologies, and their associated costs. In February 2021, MGE and its co-owner filed a CA application with the PSCW. If approved, MGE's share of the estimated costs to comply with the rule is estimated to be approximately $ 4 million. Subject to approval from the PSCW, construction is expected to begin in 2022. • The EPA's cooling water intake rules require cooling water intake structures at electric power plants to meet best technology available (BTA) standards to reduce the mortality from entrainment (drawing aquatic life into a plant's cooling system) and impingement (trapping aquatic life on screens). Blount's Wisconsin Pollution Discharge Elimination System permit assumes that the plant meets BTA for the duration of the permit, which expires in 2023. However, MGE must conduct studies of its Blount plant by the end of 2021 to help regulators determine BTA. Columbia's river intakes are subject to this rule. BTA improvements may not be required given that Columbia could be fully retired before the issuance of the next permit, which is expected to be issued in 2023 or later. MGE will continue to work with Columbia's operator to evaluate all regulatory requirements applicable to the planned retirements. MGE does not expect this rule to have a material effect on its existing plants. • Greenhouse Gas (GHG) reduction guidelines and approval criteria established under the Clean Air Act for states to use in developing plans to control GHG emissions from fossil fuel-fired electric generating units (EGUs), including existing and proposed regulations governing existing, new or modified fossil-fuel generating units. In January 2021, the U.S. Court of Appeals for the District of Columbia Circuit (D.C. Circuit) vacated and remanded to the EPA the Affordable Clean Energy Rule (ACE Rule) and the repeal of the predecessor Clean Power Plan Rule (CPP Rule), both of which regulated greenhouse gas emissions from existing electric generation units pursuant to Section 111(d) of the Clean Air Act. As a result of these legal proceedings, neither the CPP nor ACE rules are currently in effect. MGE will continue to evaluate the rule development and monitor ongoing and potential legal proceedings. • The EPA's rule to regulate ambient levels of ozone through the 2015 Ozone National Ambient Air Quality Standards (NAAQS). In May 2018, the EPA issued a final rule that designated the northeast portion of Milwaukee County as being in nonattainment with Ozone NAAQS. The Elm Road Units are located in Milwaukee County, outside the designated nonattainment area. In August 2018, several environmental groups, the City of Chicago, and the State of Illinois filed federal lawsuits challenging several of the EPA's attainment designation decisions, including the partial Milwaukee County designation as being too narrow and not sufficiently protective. In July 2020, the U.S. District Court of the District of Columbia remanded the partial Milwaukee County attainment designation back to the EPA for further explanation. MGE is monitoring the outcome of the EPA's remand analysis and how it may affect the Elm Road Units in Milwaukee County. At this time, MGE does not expect that the 2015 Ozone NAAQS will have a material effect on its existing plants based on final designations. • Rules regulating nitrogen oxide (NO x 2 The EPA's CSAPR and its progeny are a suite of interstate air pollution transport rules designed to reduce ozone and fine particulate (PM2.5) air levels in areas that the EPA has determined as being significantly impacted by pollution from upwind states. In September 2019, the D.C. Circuit remanded the rule to the EPA holding that the rule improperly provided only a partial remedy for addressing interstate transport of pollutants from upwind to downwind states. In March 2021, the EPA addressed the remand by finalizing its revised CSAPR Update Rule. The revised rule does not require further emission reductions from Wisconsin stationary sources beyond those under the original CSAPR. MGE has met its current CSAPR obligations through a combination of reduced emissions through pollution control (e.g., SCR installation at Columbia), as well as owned, received, and purchased allowances. MGE expects to meet ongoing CSAPR obligations for the foreseeable future. MGE will continue to monitor legal developments and any future updates to this rule. • The EPA's Coal Combustion Residuals Rule (CCR), which regulates coal ash from burning coal for the purpose of generating electricity as a solid waste and defines what ash use activities would be considered generally exempt beneficial reuse of coal ash. The CCR rule also regulates landfills, ash ponds, and other surface impoundments used for coal combustion residuals by regulating their design, location, monitoring, and operation. In August 2020, the EPA revised the CCR rule to require owners or operators of coal-fired power plants to stop transporting CCR and non-CCR wastewater to unlined surface impoundments. In addition, regulated entities must initiate impoundment closure as soon as feasible and in no event later than April 2021, unless the EPA grants an extension. Columbia requested an extension to comply by October 2022. The EPA will address the remaining issues on remand in a subsequent action. Review of the Elm Road Units has indicated that the costs to comply with this rule are not expected to be significant. Columbia's operator has completed a review of its system and has developed a compliance plan. In February 2021, a CA application was filed with the PSCW for approval to install technology required to cease bottom ash transport water discharges rather than extend the longevity of the ash ponds. If approved, MGE's share of the estimated costs of the project would be approximately $ 4 million. Construction is expected to be completed by the end of 2022. b. Legal Matters - MGE Energy and MGE. MGE is involved in various legal matters that are being defended and handled in the normal course of business. MGE accrues for costs that are probable of being incurred and subject to reasonable estimation. The accrued amount for these matters is not material to the financial statements. MGE does not expect the resolution of these matters to have a material adverse effect on its consolidated results of operations, financial condition, or cash flows. In January 2021, certain environmental groups filed a petition against the PSCW regarding MGE's 2021 rate settlement. MGE has intervened in the petition in cooperation with the PSCW. See Footnote 9.a. for more information regarding this matter.

Rate Matters

Rate Matters	3 Months Ended
	Mar. 31, 2021
Regulated Operations [Abstract]
Rate Matters	Rate Matters - MGE Energy and MGE. a. Rate Proceedings. In May 2021, MGE filed an application with the PSCW requesting a 5.9% increase to electric rates and a 3.0% increase to gas rates for 2022. The proposed electric and gas rate increases are primarily driven by an increase in rate base including our investments in Badger Hollow I and a new customer information system. Also driving the requested electric increase is the completion in 2020 of the one-time return of the electric excess deferred tax credit related to the 2017 Tax Act not restricted by IRS normalization rules. In its application, MGE is proposing to address potential 2023 rate changes through an electric limited rate case re-opener and a 1.65% increase in gas rates. The proposed return on common stock equity for 2022 is 9.8% based on a proposed capital structure consisting of 55.6% common equity in 2022. PSCW approval of the application is pending. A final order is expected before the end of the year. In December 2020, the PSCW approved a settlement agreement for MGE's 2021 rate case. The settlement agreement provides for a zero percent increase for electric rates and an approximately 4% increase for gas rates in 2021. The electric rate settlement includes an increase in rate base but the associated rate increase is primarily offset by lower fuel and purchase power costs and a one-time $ 18.2 million return to customers of the portion of excess deferred taxes related to the 2017 Tax Act not restricted by IRS normalization rules. As part of the settlement, the fuel rules bandwidth is set at plus or minus 1% for 2021. When compared to the 2020 rate case, the settlement included lower forecasted electric sales for 2021 to reflect changes to customer usage during the COVID-19 pandemic. The gas rate increase covers infrastructure costs and technology improvements. The settlement agreement also includes escrow accounting treatment for pension and other postretirement benefit costs, bad debt expense, and customer credit card fees. Escrow accounting treatment allows MGE to defer any difference between estimated costs in rates and actual costs incurred until its next rate filing. Any difference would be recorded as a regulatory asset or regulatory liability. The return on common stock equity for 2021 is 9.8% based on a capital structure of 55.8% common equity in 2021. On January 27, 2021, Sierra Club and Vote Solar filed a petition with the Dane County Circuit Court seeking review of the PSCW decision approving the rate settlement in MGE's 2021 rate case. The PSCW is named as the responding party; MGE is not named as a party. The petition challenges the process the PSCW used to approve the portion of the settlement relating to electric rates and the electric customer fixed charge that does not vary with usage. The requested relief is unclear. The revenue requirement approved by the PSCW in the settlement has not been challenged. The PSCW is expected to vigorously defend its approval of the rate case settlement. MGE has intervened in the proceedings to further defend the PSCW’s decision. In December 2018, the PSCW approved a settlement agreement between MGE and intervening parties in the then pending rate case. The settlement decreased electric rates by 2.24%, or $ 9.2 million, in 2019. The decrease in electric rates reflected the ongoing impacts of the 2017 Tax Act. Lower fuel costs and an increase in rate base from renewable generation assets further impacted the rate change. In 2020, electric rates decreased a further 0.84%, or $ 3.4 million, as approved by the PSCW in December 2019 in MGE's 2020 Fuel Cost Plan, which reflected lower fuel costs. The settlement agreement increased gas rates by 1.06%, or $ 1.7 million, in 2019 and 1.46%, or $ 2.4 million, in 2020. The gas increase covered infrastructure costs. It also reflected the impacts of the 2017 Tax Act. The return on common stock equity for 2019 and 2020 was 9.8% based on a capital structure consisting of 56.6% common equity in 2019 and 56.1% common equity in 2020 . b. Fuel Rules. Fuel rules require Wisconsin utilities to defer electric fuel-related costs that fall outside a symmetrical cost tolerance band around the amount approved for a utility in its annual fuel proceedings. Any over- or under-recovery of the actual costs is determined in the following year and is then reflected in future billings to electric retail customers. The fuel rules bandwidth is set at plus or minus 1% in 2021. Under fuel rules, MGE defers costs, less any excess revenues, if its actual electric fuel costs exceed 101% of the electric fuel costs allowed in its latest rate order. Excess revenues are defined as revenues in the year in question that provide MGE with a greater return on common equity than authorized by the PSCW in MGE's latest rate order. Conversely, MGE is required to defer the benefit of lower costs if actual electric fuel costs were less than 99% of the electric fuel costs allowed in that order. In 2020 the fuel rules bandwidth was set at plus or minus 2%. These costs are subject to the PSCW's annual review of fuel costs completed in the year following the deferral. The PSCW issued a final decision in the 2019 fuel rules proceedings regarding $ 1.5 million of deferred savings giving MGE the option either to use the $ 1.5 million as part of the settlement to MGE's 2021 rate case or to refund the balance to customers in October 2020. MGE elected to include the savings as part of the 2021 rate change settlement as described above, reducing electric retail rates as opposed to a one-time credit back to retail customers. There was no change to the refund in the fuel rules proceedings from the amount MGE deferred in the previous year. As of December 31, 2020, MGE had deferred $ 3.2 million of 2020 fuel-related savings. These costs will be subject to the PSCW's annual review of 2020 fuel costs, which is expected to be completed in 2021. In March 2021, as part of the 2020 fuel costs application filed with the PSCW, MGE seeks to return the 2020 fuel-related savings to customers in 2022 as part of the 2022 rate case. As of March 31, 2021, MGE had deferred $ 0.5 million of 2021 fuel savings. These costs will be subject to the PSCW's annual review of 2021 fuel costs, which is expected to be completed in 2022.

Derivative and Hedging Instrume

Derivative and Hedging Instruments	3 Months Ended
	Mar. 31, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative and Hedging Instruments	Derivative and Hedging Instruments - MGE Energy and MGE. a. Purpose. As part of its regular operations, MGE enters into contracts, including options, swaps, futures, forwards, and other contractual commitments, to manage its exposure to commodity prices. To the extent that these contracts are derivatives, MGE assesses whether or not the normal purchases or normal sales exclusion applies. For contracts to which this exclusion cannot be applied, the derivatives are recognized in the consolidated balance sheets at fair value. MGE's financial commodity derivative activities are conducted in accordance with its electric and gas risk management program, which is approved by the PSCW and limits the volume MGE can hedge with specific risk management strategies. The maximum length of time over which cash flows related to energy commodities can be hedged is four b. Notional Amounts. The gross notional volume of open derivatives is as follows: March 31, 2021 December 31, 2020 Commodity derivative contracts 277,400 MWh 259,080 MWh Commodity derivative contracts 2,190,000 Dth 6,030,000 Dth FTRs 1,152 MW 2,869 MW PPA 700 MW 850 MW c. Financial Statement Presentation. MGE purchases and sells exchange-traded and over-the-counter options, swaps, and future contracts. These arrangements are primarily entered into to help stabilize the price risk associated with gas or power purchases. These transactions are employed by both MGE's gas and electric segments. Additionally, as a result of the firm transmission agreements that MGE holds on electricity transmission paths in the MISO market, MGE holds financial transmission rights (FTRs). An FTR is a financial instrument that entitles the holder to a stream of revenues or charges based on the differences in hourly day-ahead energy prices between two points on the transmission grid. The fair values of these instruments are offset with a corresponding regulatory asset/liability depending on whether they are in a net loss/gain position. Depending on the nature of the instrument, the gain or loss associated with these transactions will be reflected as cost of gas sold, fuel for electric generation, or purchased power expense in the delivery month applicable to the instrument. As of March 31, 2021, and December 31, 2020, the fair value of exchange traded derivatives and FTRs exceeded their cost basis by $ 0.5 million and $ 0.2 million, respectively. MGE is a party to a purchased power agreement that provides MGE with firm capacity and energy during a base term from June 1, 2012, through May 31, 2022. The agreement also allows MGE an option to extend the contract after the base term. The agreement is accounted for as a derivative contract and is recognized at its fair value on the consolidated balance sheets. However, the derivative qualifies for regulatory deferral and is recognized with a corresponding regulatory asset or liability depending on whether the fair value is in a loss or gain position. The fair value of the contract as of March 31, 2021, and December 31, 2020, reflected a loss position of $ 11.6 million and $ 14.1 million, respectively. The actual cost will be recognized in purchased power expense in the month of purchase. The following table summarizes the fair value of the derivative instruments on the consolidated balance sheets. All derivative instruments in this table are presented on a gross basis and are calculated prior to the netting of instruments with the same counterparty under a master netting agreement as well as the netting of collateral. For financial statement purposes, instruments are netted with the same counterparty under a master netting agreement as well as the netting of collateral. Derivative Derivative (In thousands) Assets Liabilities Balance Sheet Location March 31, 2021 Commodity derivative contracts (a) $ 653 $ 174 Other current assets Commodity derivative contracts (a) 30 16 Other deferred charges FTRs 38 - Other current assets PPA N/A 9,790 Derivative liability (current) PPA N/A 1,800 Derivative liability (long-term) December 31, 2020 Commodity derivative contracts (a) $ 617 $ 593 Other current assets Commodity derivative contracts (a) 189 39 Other deferred charges FTRs - 23 Other current liabilities PPA N/A 10,160 Derivative liability (current) PPA N/A 3,980 Derivative liability (long-term) (a) No collateral was posted against derivative positions as of March 31, 2021, and December 31, 2020 . The following tables show the effect of netting arrangements for recognized derivative assets and liabilities that are subject to a master netting arrangement or similar arrangement on the consolidated balance sheets. Offsetting of Derivative Assets (In thousands) Gross Amounts Gross Amounts Offset in Balance Sheets Collateral Posted Against Derivative Positions Net Amount Presented in Balance Sheets March 31, 2021 Commodity derivative contracts $ 683 $ ( 190) $ - $ 493 FTRs 38 - - 38 December 31, 2020 Commodity derivative contracts $ 806 $ ( 632) $ - $ 174 Offsetting of Derivative Liabilities (In thousands) Gross Amounts Gross Amounts Offset in Balance Sheets Collateral Posted Against Derivative Positions Net Amount Presented in Balance Sheets March 31, 2021 Commodity derivative contracts $ 190 $ ( 190) $ - $ - PPA 11,590 - - 11,590 December 31, 2020 Commodity derivative contracts $ 632 $ ( 632) $ - $ - FTRs 23 - - 23 PPA 14,140 - - 14,140 The following tables summarize the unrealized and realized gains/losses related to the derivative instruments on the consolidated balance sheets and the consolidated statements of income. 2021 2020 (In thousands) Current and Long-Term Regulatory Asset Other Current Assets Current and Long-Term Regulatory Asset Other Current Assets Three Months Ended March 31: Balance at January 1, $ 13,989 $ 1,162 $ 26,875 $ 1,100 Unrealized gain ( 3,588) - ( 689) - Realized (loss) gain reclassified to a deferred account ( 50) 50 ( 1,063) 1,063 Realized gain (loss) reclassified to income statement 708 ( 1,039) 204 ( 1,733) Balance at March 31, $ 11,059 $ 173 $ 25,327 $ 430 Realized losses (gains) 2021 2020 (In thousands) Fuel for Electric Generation/ Purchased Power Cost of Gas Sold Fuel for Electric Generation/ Purchased Power Cost of Gas Sold Three Months Ended March 31: Commodity derivative contracts $ ( 195) $ 1,022 $ 680 $ 1,607 FTRs ( 256) - ( 65) - PPA ( 240) - ( 693) - MGE's commodity derivative contracts, FTRs, and PPA are subject to regulatory deferral. These derivatives are marked to fair value and are offset with a corresponding regulatory asset or liability. Realized gains and losses are deferred on the consolidated balance sheets and are recognized in earnings in the delivery month applicable to the instrument. As a result of the treatment described above, there are no unrealized gains or losses that flow through earnings. The PPA has a provision that may require MGE to post collateral if MGE's debt rating falls below investment grade (i.e., below BBB-). The amount of collateral that it may be required to post varies from $ 20.0 million to $ 40.0 million, depending on MGE's nominated capacity amount. As of March 31, 2021, no collateral was required to be, or had been, posted. Certain counterparties extend MGE a credit limit. If MGE exceeds these limits, the counterparties may require collateral to be posted. As of March 31, 2021, and December 31, 2020, no Nonperformance of counterparties to the non-exchange traded derivatives could expose MGE to credit loss. However, MGE enters into transactions only with companies that meet or exceed strict credit guidelines, and it monitors these counterparties on an ongoing basis to mitigate nonperformance risk in its portfolio. As of March 31, 2021, no counterparties had defaulted.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments - MGE Energy and MGE. Fair value is defined as the price that would be received to sell an asset or would be paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. The accounting standard clarifies that fair value should be based on the assumptions market participants would use when pricing the asset or liability including assumptions about risk. The standard also establishes a three-level fair value hierarchy based upon the observability of the assumptions used and requires the use of observable market data when available. The levels are: Level 1 - Pricing inputs are quoted prices within active markets for identical assets or liabilities. Level 2 - Pricing inputs are quoted prices within active markets for similar assets or liabilities; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations that are correlated with or otherwise verifiable by observable market data. Level 3 - Pricing inputs are unobservable and reflect management's best estimate of what market participants would use in pricing the asset or liability. a. Fair Value of Financial Assets and Liabilities Recorded at the Carrying Amount. The carrying amount of cash, cash equivalents, and outstanding commercial paper approximates fair market value due to the short maturity of those investments and obligations. The estimated fair market value of long-term debt is based on quoted market prices for similar financial instruments. Since long-term debt is not traded in an active market, it is classified as Level 2. The estimated fair market value of financial instruments are as follows: March 31, 2021 December 31, 2020 (In thousands) Carrying Amount Fair Value Carrying Amount Fair Value MGE Energy Assets: Cash and cash equivalents $ 40,239 $ 40,239 $ 44,738 $ 44,738 Liabilities: Short-term debt - commercial paper 54,000 54,000 52,500 52,500 Long-term debt (a) 527,038 590,748 528,220 639,271 MGE Assets: Cash and cash equivalents $ 6,709 $ 6,709 $ 4,103 $ 4,103 Liabilities: Short-term debt - commercial paper 54,000 54,000 52,500 52,500 Long-term debt (a) 527,038 590,748 528,220 639,271 (a) Includes long-term debt due within one year. Excludes debt issuance costs and unamortized discount of $ 4.0 million and $ 4.1 million as of March 31, 2021, and December 31, 2020, respectively. b. Recurring Fair Value Measurements. The following table presents the balances of assets and liabilities measured at fair value on a recurring basis. Fair Value as of March 31, 2021 (In thousands) Total Level 1 Level 2 Level 3 MGE Energy Assets: Derivatives, net (b) $ 721 $ 423 $ - $ 298 Exchange-traded investments 1,474 1,474 - - Total Assets $ 2,195 $ 1,897 $ - $ 298 Liabilities: Derivatives, net (b) $ 11,780 $ 115 $ - $ 11,665 Deferred compensation 3,581 - 3,581 - Total Liabilities $ 15,361 $ 115 $ 3,581 $ 11,665 MGE Assets: Derivatives, net (b) $ 721 $ 423 $ - $ 298 Exchange-traded investments 431 431 - - Total Assets $ 1,152 $ 854 $ - $ 298 Liabilities: Derivatives, net (b) $ 11,780 $ 115 $ - $ 11,665 Deferred compensation 3,581 - 3,581 - Total Liabilities $ 15,361 $ 115 $ 3,581 $ 11,665 Fair Value as of December 31, 2020 (In thousands) Total Level 1 Level 2 Level 3 MGE Energy Assets: Derivatives, net (b) $ 806 $ 436 $ - $ 370 Exchange-traded investments 1,750 1,750 - - Total Assets $ 2,556 $ 2,186 $ - $ 370 Liabilities: Derivatives, net (b) $ 14,795 $ 370 $ - $ 14,425 Deferred compensation 3,509 - 3,509 - Total Liabilities $ 18,304 $ 370 $ 3,509 $ 14,425 MGE Assets: Derivatives, net (b) $ 806 $ 436 $ - $ 370 Exchange-traded investments 603 603 - - Total Assets $ 1,409 $ 1,039 $ - $ 370 Liabilities: Derivatives, net (b) $ 14,795 $ 370 $ - $ 14,425 Deferred compensation 3,509 - 3,509 - Total Liabilities $ 18,304 $ 370 $ 3,509 $ 14,425 (b) These amounts are shown gross. No collateral was posted against derivative positions with counterparties as of March 31, 2021, or December 31, 2020. Investments include exchange-traded investment securities valued using quoted prices on active exchanges and are therefore classified as Level 1. The deferred compensation plan allows participants to defer certain cash compensation into a notional investment account. These amounts are included within other deferred liabilities in the consolidated balance sheets. The notional investments earn interest based upon the semiannual rate of U.S. Treasury Bills having a 26 1% compounded monthly with a minimum annual rate of 7%, compounded monthly. The notional investments are based upon observable market data, however, since the deferred compensation obligations themselves are not exchanged in an active market, they are classified as Level 2. Derivatives include exchange-traded derivative contracts, over-the-counter transactions, a purchased power agreement, and FTRs. Most exchange-traded derivative contracts are valued based on unadjusted quoted prices in active markets and are therefore classified as Level 1. A small number of exchange-traded derivative contracts are valued using quoted market pricing in markets with insufficient volumes and are therefore considered unobservable and classified as Level 3. Transactions done with an over-the-counter party are on inactive markets and are therefore classified as Level 3. These transactions are valued based on quoted prices from markets with similar exchange-traded transactions. FTRs are priced based upon monthly auction results for identical or similar instruments in a closed market with limited data available and are therefore classified as Level 3. The purchased power agreement (see Footnote 10) was valued using an internal pricing model and therefore is classified as Level 3. The model projects future market energy prices and compares those prices to the projected power costs to be incurred under the contract. Inputs to the model require significant management judgment and estimation. Future energy prices are based on a forward power pricing curve using exchange-traded contracts in the electric futures market. A basis adjustment is applied to the market energy price to reflect the price differential between the market price delivery point and the counterparty delivery point. The historical relationship between the delivery points is reviewed and a discount (below 100%) or premium (above 100%) is derived. This comparison is done for both peak times when demand is high and off-peak times when demand is low. If the basis adjustment is lowered, the fair value measurement will decrease, and if the basis adjustment is increased, the fair value measurement will increase. The projected power costs anticipated to be incurred under the purchased power agreement are determined using many factors, including historical generating costs, future prices, and expected fuel mix of the counterparty. An increase in the projected fuel costs would result in a decrease in the fair value measurement of the purchased power agreement. A significant input that MGE estimates is the counterparty's fuel mix in determining the projected power cost. MGE also considers the assumptions that market participants would use in valuing the asset or liability. This consideration includes assumptions about market risk such as liquidity, volatility, and contract duration. The fair value model uses a discount rate that incorporates discounting, credit, and model risks. The following table presents the significant unobservable inputs used in the pricing model. Model Input Significant Unobservable Inputs March 31, 2021 December 31, 2020 Basis adjustment: On peak 94.4 % 94.2 % Off peak 95.0 % 94.5 % Counterparty fuel mix: Internal generation - range 41.0% - 66.0 % 46.0% - 65.0 % Internal generation - weighted average 56.9 % 56.5 % Purchased power - range 59.0% - 34.0 % 54.0% - 35.0 % Purchased power - weighted average 43.1 % 43.5 % The following table summarizes the changes in Level 3 commodity derivative assets and liabilities measured at fair value on a recurring basis. Three Months Ended March 31, (In thousands) 2021 2020 Beginning balance $ ( 14,055) $ ( 26,456) Realized and unrealized gains (losses): Included in regulatory assets 2,688 810 Included in other comprehensive income - - Included in earnings 307 ( 1,453) Included in current assets 355 247 Purchases 5,884 5,015 Sales - - Issuances - - Settlements ( 6,546) ( 3,810) Balance as of March 31, $ ( 11,367) $ ( 25,647) Total gains (losses) included in earnings attributed to the change in unrealized gains (losses) related to assets and liabilities held at March 31, (c) $ - $ - The following table presents total realized and unrealized gains (losses) included in income for Level 3 assets and liabilities measured at fair value on a recurring basis (c) Three Months Ended March 31, (In thousands) 2021 2020 Purchased power expense $ 702 $ ( 1,184) Cost of gas sold expense ( 395) ( 269) Total $ 307 $ ( 1,453) (c) MGE's exchange-traded derivative contracts, over-the-counter party transactions, purchased power agreement, and FTRs are subject to regulatory deferral. These derivatives are therefore marked to fair value and are offset in the financial statements with a corresponding regulatory asset or liability.

Joint Plant Ownership

Joint Plant Ownership	3 Months Ended
	Mar. 31, 2021
Public Utilities Property Plant And Equipment [Abstract]
Jointly Owned Electric Utility Plant	Joint Plant Ownership - MGE Energy and MGE MGE currently has ongoing jointly-owned solar generation construction projects, as shown in the following table. Incurred costs are reflected in "Construction work in progress" on the consolidated balance sheets. Ownership Share of Share of Costs incurred as of Date of Commercial Project Interest Generation Estimated Costs March 31, 2021 (a) Operation Badger Hollow I (b) 33 % 50 MW $ 65 million $ 56.4 million Q3 2021 (c) Badger Hollow II (b) 33 % 50 MW $ 65 million $ 5.3 million December 2022 (c) (a) Excluding AFUDC. (b) The Badger Hollow I and Badger Hollow II solar farms are located in southwestern Wisconsin in Iowa County, near the villages of Montfort and Cobb. (c) Estimated date of commercial operation. MGE received specific approval to recover 100% AFUDC on each of these projects. During the three months ended March 31, 2021 and 2020, MGE recognized $ 1.1 million and $ 0.4 million, respectively, after tax, in AFUDC for Badger Hollow I and II .

Revenue

Revenue	3 Months Ended
	Mar. 31, 2021
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer	Revenue - MGE Energy and MGE. Revenues disaggregated by revenue source were as follows: Three Months Ended (In thousands) March 31, Electric revenues 2021 2020 Residential $ 36,694 $ 33,428 Commercial 47,883 47,634 Industrial 3,001 2,800 Other-retail/municipal 8,170 8,204 Total retail 95,748 92,066 Sales to the market 4,639 482 Other revenues 222 442 Total electric revenues $ 100,609 $ 92,990 Gas revenues Residential 39,758 33,487 Commercial/Industrial 25,507 21,471 Total retail 65,265 54,958 Gas transportation 2,002 1,794 Other revenues 3 93 Total gas revenues $ 67,270 $ 56,845 Non-regulated energy revenues 36 38 Total Operating Revenue $ 167,915 $ 149,873 Performance Obligations A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account. A contract's transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. The majority of contracts have a single performance obligation. Retail Revenue (Residential, Commercial, Industrial, and Other Retail/Municipal) Providing electric and gas utility service to retail customers represents MGE's core business activity. Tariffs are approved by the PSCW through a rate order and provide MGE's customers with the standard terms and conditions, including pricing terms. The performance obligation to deliver electricity or gas is satisfied over time as the customer simultaneously receives and consumes the commodities provided by MGE. MGE recognizes revenues as the commodity is delivered to customers. Meters are read on a systematic basis throughout the month based on established meter-reading schedules and customers are subsequently billed for services received. At the end of the month, MGE accrues an estimate for unbilled commodities delivered to customers. The unbilled revenue estimate is based on daily system demand volumes, weather factors, estimated line losses, estimated customer usage by class, and applicable customer rates. Utility Cost Recovery Mechanisms MGE's tariff rates include a provision for fuel cost recovery. The PSCW allows Wisconsin utilities to defer electric fuel-related costs, less excess revenues, that fall outside a symmetrical cost tolerance band. Any over- or under-recovery of the actual costs in a given year is determined in the following year and is then reflected in future billings to electric retail customers. Over-collection of fuel-related costs that are outside the approved range will be recognized as a reduction of revenue. Under-collection of these costs will be recognized in "Purchased power" expense in the consolidated statements of income. The cumulative effects of these deferred amounts will be recorded in "Regulatory assets" or "Regulatory liabilities" on the consolidated balance sheets until they are reflected in future billings to customers. See Footnote 9.b. for further information. MGE also has other cost recovery mechanisms. For example, any over-collection of the difference between actual costs incurred and the amount of costs collected from customers is recorded as a reduction of revenue in the period incurred. Sales to the Market Sales to the market include energy charges, capacity or demand charges, and ancillary charges represented by wholesale sales of electricity made to third parties who are not ultimate users of the electricity. Most of these sales are spot market transactions on the markets operated by MISO. Each transaction is considered a performance obligation and revenue is recognized in the period in which energy charges, capacity or demand charges, and ancillary services are sold into MISO. MGE reports, on a net basis, transactions on the MISO markets in which it buys and sells power within the same hour to meet electric energy delivery requirements. Transportation of Gas MGE has contracts under which it provides gas transportation services to customers who have elected to purchase gas from a third party MGE delivers this gas via pipelines within its service territory. Revenue is recognized as service is rendered or gas is delivered to customers. Tariffs are approved by the PSCW through a rate order and provide gas transportation customers with standard terms and conditions, including pricing terms.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Segment Information	Segment Information - MGE Energy and MGE. MGE Energy operates in the following business segments: electric utility, gas utility, nonregulated energy, transmission investment, and all other. See the 2020 Annual Report on Form 10-K for additional discussion of each of these segments. The following tables show segment information for MGE Energy's operations for the indicated periods: (In thousands) MGE Energy Electric Gas Nonregulated Energy Transmission Investment All Others Consolidation/ Elimination Consolidated Total Three Months Ended March 31, 2021 Operating revenues from external customers $ 100,609 $ 67,270 $ 36 $ - $ - $ - $ 167,915 Interdepartmental revenues 273 4,811 10,173 - - ( 15,257) - Total operating revenues 100,882 72,081 10,209 - - ( 15,257) 167,915 Equity in earnings of investments - - - 2,444 - - 2,444 Net income (loss) 18,024 10,556 5,194 1,778 ( 619) - 34,933 Three Months Ended March 31, 2020 Operating revenues from external customers $ 92,990 $ 56,845 $ 38 $ - $ - $ - $ 149,873 Interdepartmental revenues 191 3,451 10,056 - - ( 13,698) - Total operating revenues 93,181 60,296 10,094 - - ( 13,698) 149,873 Equity in earnings of investments - - - 2,286 - - 2,286 Net income (loss) 11,463 8,034 5,060 1,663 ( 183) - 26,037 The following tables show segment information for MGE's operations for the indicated periods: (In thousands) MGE Electric Gas Nonregulated Energy Consolidation/ Elimination Consolidated Total Three Months Ended March 31, 2021 Operating revenues from external customers $ 100,609 $ 67,270 $ 36 $ - $ 167,915 Interdepartmental revenues 273 4,811 10,173 ( 15,257) - Total operating revenues 100,882 72,081 10,209 ( 15,257) 167,915 Net income attributable to MGE 18,024 10,556 5,194 ( 5,501) 28,273 Three Months Ended March 31, 2020 Operating revenues from external customers $ 92,990 $ 56,845 $ 38 $ - $ 149,873 Interdepartmental revenues 191 3,451 10,056 ( 13,698) - Total operating revenues 93,181 60,296 10,094 ( 13,698) 149,873 Net income attributable to MGE 11,463 8,034 5,060 ( 5,493) 19,064

Significant Accounting Policies

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Variable Interest Entities	MGE Power Elm Road and MGE Power West Campus own electric generating assets and lease those assets to MGE. Both entities are variable interest entities under applicable authoritative accounting guidance. MGE is considered the primary beneficiary of these entities as a result of contractual agreements. As a result, MGE has consolidated MGE Power Elm Road and MGE Power West Campus.
Cash and Cash Equivalents	Cash Equivalents All highly liquid investments purchased with an original maturity of three months or less to be cash equivalents.
Restricted Cash	Restricted Cash MGE has certain cash accounts that are restricted to uses other than current operations and designated for a specific purpose. MGE's restricted cash accounts include cash held by trustees for certain employee benefits and cash deposits held by third parties. These are included in "Other current assets" on the consolidated balance sheets.
Receivable Margin Account	Receivable – Margin Account Cash amounts held by counterparties as margin collateral for certain financial transactions are recorded as Receivable – margin account in "Other current assets" on the consolidated balance sheets. The costs being hedged are fuel for electric generation, purchased power, and cost of gas sold.
New Accounting Pronouncements Disclosure	New Accounting Standards - MGE Energy and MGE. MGE Energy and MGE reviewed FASB authoritative guidance recently issued, none of which are expected to have a material impact on the consolidated results of operations, financial condition, or cash flows.
Investments - ATC and ATC Holdco	MGE Transco and MGEE Transco have accounted for their investments in ATC and ATC Holdco, respectively, under the equity method of accounting.
Pension and Other Postretirement Benefit Plan Assets	MGE maintains qualified and nonqualified pension plans, health care, and life insurance benefits and defined contribution 401(k) benefit plans for its employees and retirees. The components of net periodic benefit cost, other than the service cost component, are recorded in " Other income, net " on the consolidated statements of income. The service cost component is recorded in " Other operations and maintenance " on the consolidated statements of income. MGE has regulatory treatment and recognizes regulatory assets or liabilities for timing differences between when net periodic benefit costs are recovered and when costs are recognized.
Common Stock	MGE Energy sells shares of its common stock through its Direct Stock Purchase and Dividend Reinvestment Plan (the Stock Plan). Those shares may be newly issued shares or shares that are purchased in the open market by an independent agent for participants in the Stock Plan. All sales under the Stock Plan are covered by a shelf registration statement that MGE Energy filed with the SEC.
Wisconsin Fuel Rules	Fuel rules require Wisconsin utilities to defer electric fuel-related costs that fall outside a symmetrical cost tolerance band around the amount approved for a utility in its annual fuel proceedings. Any over- or under-recovery of the actual costs is determined in the following year and is then reflected in future billings to electric retail customers. The fuel rules bandwidth is set at plus or minus 1% in 2021. Under fuel rules, MGE defers costs, less any excess revenues, if its actual electric fuel costs exceed 101% of the electric fuel costs allowed in its latest rate order. Excess revenues are defined as revenues in the year in question that provide MGE with a greater return on common equity than authorized by the PSCW in MGE's latest rate order. Conversely, MGE is required to defer the benefit of lower costs if actual electric fuel costs were less than 99% of the electric fuel costs allowed in that order. In 2020 the fuel rules bandwidth was set at plus or minus 2%. These costs are subject to the PSCW's annual review of fuel costs completed in the year following the deferral.
Derivative Hedging	As part of its regular operations, MGE enters into contracts, including options, swaps, futures, forwards, and other contractual commitments, to manage its exposure to commodity prices. To the extent that these contracts are derivatives, MGE assesses whether or not the normal purchases or normal sales exclusion applies. For contracts to which this exclusion cannot be applied, the derivatives are recognized in the consolidated balance sheets at fair value. MGE's financial commodity derivative activities are conducted in accordance with its electric and gas risk management program, which is approved by the PSCW and limits the volume MGE can hedge with specific risk management strategies. The maximum length of time over which cash flows related to energy commodities can be hedged is four
Derivative Netting	All derivative instruments in this table are presented on a gross basis and are calculated prior to the netting of instruments with the same counterparty under a master netting agreement as well as the netting of collateral. For financial statement purposes, instruments are netted with the same counterparty under a master netting agreement as well as the netting of collateral.
Recurring Fair Value Measurements	Fair value is defined as the price that would be received to sell an asset or would be paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. The accounting standard clarifies that fair value should be based on the assumptions market participants would use when pricing the asset or liability including assumptions about risk. The standard also establishes a three-level fair value hierarchy based upon the observability of the assumptions used and requires the use of observable market data when available. The levels are: Level 1 - Pricing inputs are quoted prices within active markets for identical assets or liabilities. Level 2 - Pricing inputs are quoted prices within active markets for similar assets or liabilities; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations that are correlated with or otherwise verifiable by observable market data. Level 3 - Pricing inputs are unobservable and reflect management's best estimate of what market participants would use in pricing the asset or liability. The carrying amount of cash, cash equivalents, and outstanding commercial paper approximates fair market value due to the short maturity of those investments and obligations. The estimated fair market value of long-term debt is based on quoted market prices for similar financial instruments. Since long-term debt is not traded in an active market, it is classified as Level 2. Investments include exchange-traded investment securities valued using quoted prices on active exchanges and are therefore classified as Level 1. The deferred compensation plan allows participants to defer certain cash compensation into a notional investment account. These amounts are included within other deferred liabilities in the consolidated balance sheets. The notional investments earn interest based upon the semiannual rate of U.S. Treasury Bills having a 26 1% compounded monthly with a minimum annual rate of 7%, compounded monthly. The notional investments are based upon observable market data, however, since the deferred compensation obligations themselves are not exchanged in an active market, they are classified as Level 2. Derivatives include exchange-traded derivative contracts, over-the-counter transactions, a purchased power agreement, and FTRs. Most exchange-traded derivative contracts are valued based on unadjusted quoted prices in active markets and are therefore classified as Level 1. A small number of exchange-traded derivative contracts are valued using quoted market pricing in markets with insufficient volumes and are therefore considered unobservable and classified as Level 3. Transactions done with an over-the-counter party are on inactive markets and are therefore classified as Level 3. These transactions are valued based on quoted prices from markets with similar exchange-traded transactions. FTRs are priced based upon monthly auction results for identical or similar instruments in a closed market with limited data available and are therefore classified as Level 3. The purchased power agreement (see Footnote 10) was valued using an internal pricing model and therefore is classified as Level 3. The model projects future market energy prices and compares those prices to the projected power costs to be incurred under the contract. Inputs to the model require significant management judgment and estimation. Future energy prices are based on a forward power pricing curve using exchange-traded contracts in the electric futures market. A basis adjustment is applied to the market energy price to reflect the price differential between the market price delivery point and the counterparty delivery point. The historical relationship between the delivery points is reviewed and a discount (below 100%) or premium (above 100%) is derived. This comparison is done for both peak times when demand is high and off-peak times when demand is low. If the basis adjustment is lowered, the fair value measurement will decrease, and if the basis adjustment is increased, the fair value measurement will increase. The projected power costs anticipated to be incurred under the purchased power agreement are determined using many factors, including historical generating costs, future prices, and expected fuel mix of the counterparty. An increase in the projected fuel costs would result in a decrease in the fair value measurement of the purchased power agreement. A significant input that MGE estimates is the counterparty's fuel mix in determining the projected power cost. MGE also considers the assumptions that market participants would use in valuing the asset or liability. This consideration includes assumptions about market risk such as liquidity, volatility, and contract duration. The fair value model uses a discount rate that incorporates discounting, credit, and model risks. The following table presents the significant unobservable inputs used in the pricing model. Model Input Significant Unobservable Inputs March 31, 2021 December 31, 2020 Basis adjustment: On peak 94.4 % 94.2 % Off peak 95.0 % 94.5 % Counterparty fuel mix: Internal generation - range 41.0% - 66.0 % 46.0% - 65.0 % Internal generation - weighted average 56.9 % 56.5 % Purchased power - range 59.0% - 34.0 % 54.0% - 35.0 % Purchased power - weighted average 43.1 % 43.5 %
Revenue Recognition	Performance Obligations A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account. A contract's transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. The majority of contracts have a single performance obligation. Retail Revenue (Residential, Commercial, Industrial, and Other Retail/Municipal) Providing electric and gas utility service to retail customers represents MGE's core business activity. Tariffs are approved by the PSCW through a rate order and provide MGE's customers with the standard terms and conditions, including pricing terms. The performance obligation to deliver electricity or gas is satisfied over time as the customer simultaneously receives and consumes the commodities provided by MGE. MGE recognizes revenues as the commodity is delivered to customers. Meters are read on a systematic basis throughout the month based on established meter-reading schedules and customers are subsequently billed for services received. At the end of the month, MGE accrues an estimate for unbilled commodities delivered to customers. The unbilled revenue estimate is based on daily system demand volumes, weather factors, estimated line losses, estimated customer usage by class, and applicable customer rates. Utility Cost Recovery Mechanisms MGE's tariff rates include a provision for fuel cost recovery. The PSCW allows Wisconsin utilities to defer electric fuel-related costs, less excess revenues, that fall outside a symmetrical cost tolerance band. Any over- or under-recovery of the actual costs in a given year is determined in the following year and is then reflected in future billings to electric retail customers. Over-collection of fuel-related costs that are outside the approved range will be recognized as a reduction of revenue. Under-collection of these costs will be recognized in "Purchased power" expense in the consolidated statements of income. The cumulative effects of these deferred amounts will be recorded in "Regulatory assets" or "Regulatory liabilities" on the consolidated balance sheets until they are reflected in future billings to customers. See Footnote 9.b. for further information. MGE also has other cost recovery mechanisms. For example, any over-collection of the difference between actual costs incurred and the amount of costs collected from customers is recorded as a reduction of revenue in the period incurred. Sales to the Market Sales to the market include energy charges, capacity or demand charges, and ancillary charges represented by wholesale sales of electricity made to third parties who are not ultimate users of the electricity. Most of these sales are spot market transactions on the markets operated by MISO. Each transaction is considered a performance obligation and revenue is recognized in the period in which energy charges, capacity or demand charges, and ancillary services are sold into MISO. MGE reports, on a net basis, transactions on the MISO markets in which it buys and sells power within the same hour to meet electric energy delivery requirements. Transportation of Gas MGE has contracts under which it provides gas transportation services to customers who have elected to purchase gas from a third party MGE delivers this gas via pipelines within its service territory. Revenue is recognized as service is rendered or gas is delivered to customers. Tariffs are approved by the PSCW through a rate order and provide gas transportation customers with standard terms and conditions, including pricing terms.

Summary of Significant Accoun_2

Summary of Significant Accounting Principles (Tables)	3 Months Ended
	Mar. 31, 2021
Cash, Cash Equivalents, And Restricted Cash [Abstract]
Cash, Cash Equivalents, and Restricted Cash	The following table presents the components of total cash, cash equivalents, and restricted cash on the consolidated balance sheets. MGE Energy MGE March 31, December 31, March 31, December 31, (In thousands) 2021 2020 2021 2020 Cash and cash equivalents $ 40,239 $ 44,738 $ 6,709 $ 4,103 Restricted cash 467 644 467 644 Receivable - margin account 796 1,657 796 1,657 Cash, cash equivalents, and restricted cash $ 41,502 $ 47,039 $ 7,972 $ 6,404

Investment in ATC and ATC Hol_2

Investment in ATC and ATC Holdco (Tables)	3 Months Ended
	Mar. 31, 2021
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments Financial Data	MGE Transco and MGEE Transco have accounted for their investments in ATC and ATC Holdco, respectively, under the equity method of accounting. Equity earnings from investments are recorded as "Other income" on the consolidated statements of income of MGE Energy. MGE Transco recorded the following amounts related to its investment in ATC: Three Months Ended March 31, (In thousands) 2021 2020 Equity earnings from investment in ATC $ 2,420 $ 2,266 Dividends from ATC 1,967 2,391 Capital contributions to ATC - 178 ATC ' s summarized financial data is as follows: Three Months Ended March 31, (In thousands) 2021 2020 Operating revenues $ 188,694 $ 186,801 Operating expenses ( 95,104) ( 95,211) Other income, net 378 375 Interest expense, net ( 28,871) ( 28,888) Earnings before members' income taxes $ 65,097 $ 63,077

Taxes (Tables)

Taxes (Tables)	3 Months Ended
	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Effective Tax Rate Reconciliation	The consolidated income tax provision differs from the amount computed by applying the statutory federal income tax rate to income before income taxes, as follows: MGE Energy MGE Three Months Ended March 31, 2021 2020 2021 2020 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefit 6.3 6.3 6.3 6.3 Amortized investment tax credits ( 1.6) ( 0.1) ( 1.8) ( 0.1) Credit for electricity from wind energy ( 7.1) ( 6.9) ( 7.8) ( 7.5) AFUDC equity, net ( 0.6) ( 1.6) ( 0.6) ( 1.7) Amortization of utility excess deferred tax - tax reform (a) ( 16.7) ( 2.6) ( 18.3) ( 2.8) Other, net, individually insignificant - - ( 0.1) ( 0.1) Effective income tax rate 1.3 % 16.1 % ( 1.3) % 15.1 % (a) Included are impacts of the 2017 Tax Act for the regulated utility for excess deferred taxes recognized using a normalization method of accounting in recognition of IRS rules that restrict the rate at which the excess deferred taxes may be returned to utility customers. For the three months ended March 31, 2021 and 2020, MGE recognized $ 0.7 million. Included in the 2021 rate settlement was a one-time return to customers of the electric portion of excess deferred taxes related to the 2017 Tax Act not restricted by IRS normalization rules. For the three months ended March 31, 2021, MGE recognized $ 3.3 million.

Pension and Other Postretirem_2

Pension and Other Postretirement Plans (Tables)	3 Months Ended
	Mar. 31, 2021
Compensation and Retirement Disclosure [Abstract]
Schedule of Net Periodic Benefit Costs	The following table presents the components of net periodic benefit costs recognized. Three Months Ended March 31, (In thousands) 2021 2020 Pension Benefits Components of net periodic benefit cost: Service cost $ 1,422 $ 1,316 Interest cost 2,272 3,023 Expected return on assets ( 7,375) ( 6,811) Amortization of: Prior service credit ( 31) ( 31) Actuarial loss 1,580 1,286 Net periodic benefit (credit) cost $ ( 2,132) $ ( 1,217) Postretirement Benefits Components of net periodic benefit cost: Service cost $ 351 $ 311 Interest cost 384 573 Expected return on assets ( 817) ( 790) Amortization of: Transition obligation 1 1 Prior service credit ( 380) ( 667) Actuarial loss 109 70 Net periodic benefit (credit) cost $ ( 352) $ ( 502)

Derivative and Hedging Instru_2

Derivative and Hedging Instruments (Tables)	3 Months Ended
	Mar. 31, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gross Notional Volume of Open Derivatives	The gross notional volume of open derivatives is as follows: March 31, 2021 December 31, 2020 Commodity derivative contracts 277,400 MWh 259,080 MWh Commodity derivative contracts 2,190,000 Dth 6,030,000 Dth FTRs 1,152 MW 2,869 MW PPA 700 MW 850 MW
Fair Value of Derivative Instruments on the Balance Sheet	The following table summarizes the fair value of the derivative instruments on the consolidated balance sheets. All derivative instruments in this table are presented on a gross basis and are calculated prior to the netting of instruments with the same counterparty under a master netting agreement as well as the netting of collateral. For financial statement purposes, instruments are netted with the same counterparty under a master netting agreement as well as the netting of collateral. Derivative Derivative (In thousands) Assets Liabilities Balance Sheet Location March 31, 2021 Commodity derivative contracts (a) $ 653 $ 174 Other current assets Commodity derivative contracts (a) 30 16 Other deferred charges FTRs 38 - Other current assets PPA N/A 9,790 Derivative liability (current) PPA N/A 1,800 Derivative liability (long-term) December 31, 2020 Commodity derivative contracts (a) $ 617 $ 593 Other current assets Commodity derivative contracts (a) 189 39 Other deferred charges FTRs - 23 Other current liabilities PPA N/A 10,160 Derivative liability (current) PPA N/A 3,980 Derivative liability (long-term) (a) No collateral was posted against derivative positions as of March 31, 2021, and December 31, 2020 .
Offsetting Assets	The following tables show the effect of netting arrangements for recognized derivative assets and liabilities that are subject to a master netting arrangement or similar arrangement on the consolidated balance sheets. Offsetting of Derivative Assets (In thousands) Gross Amounts Gross Amounts Offset in Balance Sheets Collateral Posted Against Derivative Positions Net Amount Presented in Balance Sheets March 31, 2021 Commodity derivative contracts $ 683 $ ( 190) $ - $ 493 FTRs 38 - - 38 December 31, 2020 Commodity derivative contracts $ 806 $ ( 632) $ - $ 174
Offsetting Liabilities	Offsetting of Derivative Liabilities (In thousands) Gross Amounts Gross Amounts Offset in Balance Sheets Collateral Posted Against Derivative Positions Net Amount Presented in Balance Sheets March 31, 2021 Commodity derivative contracts $ 190 $ ( 190) $ - $ - PPA 11,590 - - 11,590 December 31, 2020 Commodity derivative contracts $ 632 $ ( 632) $ - $ - FTRs 23 - - 23 PPA 14,140 - - 14,140
Derivative Gains and Losses in Balance Sheet	The following tables summarize the unrealized and realized gains/losses related to the derivative instruments on the consolidated balance sheets and the consolidated statements of income. 2021 2020 (In thousands) Current and Long-Term Regulatory Asset Other Current Assets Current and Long-Term Regulatory Asset Other Current Assets Three Months Ended March 31: Balance at January 1, $ 13,989 $ 1,162 $ 26,875 $ 1,100 Unrealized gain ( 3,588) - ( 689) - Realized (loss) gain reclassified to a deferred account ( 50) 50 ( 1,063) 1,063 Realized gain (loss) reclassified to income statement 708 ( 1,039) 204 ( 1,733) Balance at March 31, $ 11,059 $ 173 $ 25,327 $ 430
Derivative Gains and Losses in Income Statement	Realized losses (gains) 2021 2020 (In thousands) Fuel for Electric Generation/ Purchased Power Cost of Gas Sold Fuel for Electric Generation/ Purchased Power Cost of Gas Sold Three Months Ended March 31: Commodity derivative contracts $ ( 195) $ 1,022 $ 680 $ 1,607 FTRs ( 256) - ( 65) - PPA ( 240) - ( 693) -

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Estimated Fair Market Value of Financial Instruments	The estimated fair market value of financial instruments are as follows: March 31, 2021 December 31, 2020 (In thousands) Carrying Amount Fair Value Carrying Amount Fair Value MGE Energy Assets: Cash and cash equivalents $ 40,239 $ 40,239 $ 44,738 $ 44,738 Liabilities: Short-term debt - commercial paper 54,000 54,000 52,500 52,500 Long-term debt (a) 527,038 590,748 528,220 639,271 MGE Assets: Cash and cash equivalents $ 6,709 $ 6,709 $ 4,103 $ 4,103 Liabilities: Short-term debt - commercial paper 54,000 54,000 52,500 52,500 Long-term debt (a) 527,038 590,748 528,220 639,271 (a) Includes long-term debt due within one year. Excludes debt issuance costs and unamortized discount of $ 4.0 million and $ 4.1 million as of March 31, 2021, and December 31, 2020, respectively.
Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following table presents the balances of assets and liabilities measured at fair value on a recurring basis. Fair Value as of March 31, 2021 (In thousands) Total Level 1 Level 2 Level 3 MGE Energy Assets: Derivatives, net (b) $ 721 $ 423 $ - $ 298 Exchange-traded investments 1,474 1,474 - - Total Assets $ 2,195 $ 1,897 $ - $ 298 Liabilities: Derivatives, net (b) $ 11,780 $ 115 $ - $ 11,665 Deferred compensation 3,581 - 3,581 - Total Liabilities $ 15,361 $ 115 $ 3,581 $ 11,665 MGE Assets: Derivatives, net (b) $ 721 $ 423 $ - $ 298 Exchange-traded investments 431 431 - - Total Assets $ 1,152 $ 854 $ - $ 298 Liabilities: Derivatives, net (b) $ 11,780 $ 115 $ - $ 11,665 Deferred compensation 3,581 - 3,581 - Total Liabilities $ 15,361 $ 115 $ 3,581 $ 11,665 Fair Value as of December 31, 2020 (In thousands) Total Level 1 Level 2 Level 3 MGE Energy Assets: Derivatives, net (b) $ 806 $ 436 $ - $ 370 Exchange-traded investments 1,750 1,750 - - Total Assets $ 2,556 $ 2,186 $ - $ 370 Liabilities: Derivatives, net (b) $ 14,795 $ 370 $ - $ 14,425 Deferred compensation 3,509 - 3,509 - Total Liabilities $ 18,304 $ 370 $ 3,509 $ 14,425 MGE Assets: Derivatives, net (b) $ 806 $ 436 $ - $ 370 Exchange-traded investments 603 603 - - Total Assets $ 1,409 $ 1,039 $ - $ 370 Liabilities: Derivatives, net (b) $ 14,795 $ 370 $ - $ 14,425 Deferred compensation 3,509 - 3,509 - Total Liabilities $ 18,304 $ 370 $ 3,509 $ 14,425 (b) These amounts are shown gross. No collateral was posted against derivative positions with counterparties as of March 31, 2021, or December 31, 2020.
Significant Unobservable Inputs	The following table presents the significant unobservable inputs used in the pricing model. Model Input Significant Unobservable Inputs March 31, 2021 December 31, 2020 Basis adjustment: On peak 94.4 % 94.2 % Off peak 95.0 % 94.5 % Counterparty fuel mix: Internal generation - range 41.0% - 66.0 % 46.0% - 65.0 % Internal generation - weighted average 56.9 % 56.5 % Purchased power - range 59.0% - 34.0 % 54.0% - 35.0 % Purchased power - weighted average 43.1 % 43.5 %
Changes in Level 3 Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following table summarizes the changes in Level 3 commodity derivative assets and liabilities measured at fair value on a recurring basis. Three Months Ended March 31, (In thousands) 2021 2020 Beginning balance $ ( 14,055) $ ( 26,456) Realized and unrealized gains (losses): Included in regulatory assets 2,688 810 Included in other comprehensive income - - Included in earnings 307 ( 1,453) Included in current assets 355 247 Purchases 5,884 5,015 Sales - - Issuances - - Settlements ( 6,546) ( 3,810) Balance as of March 31, $ ( 11,367) $ ( 25,647) Total gains (losses) included in earnings attributed to the change in unrealized gains (losses) related to assets and liabilities held at March 31, (c) $ - $ - (c) MGE's exchange-traded derivative contracts, over-the-counter party transactions, purchased power agreement, and FTRs are subject to regulatory deferral. These derivatives are therefore marked to fair value and are offset in the financial statements with a corresponding regulatory asset or liability.
Gains and Losses Included in Income for Level 3 Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following table presents total realized and unrealized gains (losses) included in income for Level 3 assets and liabilities measured at fair value on a recurring basis (c) Three Months Ended March 31, (In thousands) 2021 2020 Purchased power expense $ 702 $ ( 1,184) Cost of gas sold expense ( 395) ( 269) Total $ 307 $ ( 1,453) (c) MGE's exchange-traded derivative contracts, over-the-counter party transactions, purchased power agreement, and FTRs are subject to regulatory deferral. These derivatives are therefore marked to fair value and are offset in the financial statements with a corresponding regulatory asset or liability.

Joint Plant (Tables)

Joint Plant (Tables)	3 Months Ended
	Mar. 31, 2021
Public Utilities Property Plant And Equipment [Abstract]
Schedule Of Jointly Owned Utility Plants	MGE currently has ongoing jointly-owned solar generation construction projects, as shown in the following table. Incurred costs are reflected in "Construction work in progress" on the consolidated balance sheets. Ownership Share of Share of Costs incurred as of Date of Commercial Project Interest Generation Estimated Costs March 31, 2021 (a) Operation Badger Hollow I (b) 33 % 50 MW $ 65 million $ 56.4 million Q3 2021 (c) Badger Hollow II (b) 33 % 50 MW $ 65 million $ 5.3 million December 2022 (c) (a) Excluding AFUDC. (b) The Badger Hollow I and Badger Hollow II solar farms are located in southwestern Wisconsin in Iowa County, near the villages of Montfort and Cobb. (c) Estimated date of commercial operation.

Revenue (Tables)

Revenue (Tables)	3 Months Ended
	Mar. 31, 2021
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	Revenues disaggregated by revenue source were as follows: Three Months Ended (In thousands) March 31, Electric revenues 2021 2020 Residential $ 36,694 $ 33,428 Commercial 47,883 47,634 Industrial 3,001 2,800 Other-retail/municipal 8,170 8,204 Total retail 95,748 92,066 Sales to the market 4,639 482 Other revenues 222 442 Total electric revenues $ 100,609 $ 92,990 Gas revenues Residential 39,758 33,487 Commercial/Industrial 25,507 21,471 Total retail 65,265 54,958 Gas transportation 2,002 1,794 Other revenues 3 93 Total gas revenues $ 67,270 $ 56,845 Non-regulated energy revenues 36 38 Total Operating Revenue $ 167,915 $ 149,873

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Segment Information	The following tables show segment information for MGE Energy's operations for the indicated periods: (In thousands) MGE Energy Electric Gas Nonregulated Energy Transmission Investment All Others Consolidation/ Elimination Consolidated Total Three Months Ended March 31, 2021 Operating revenues from external customers $ 100,609 $ 67,270 $ 36 $ - $ - $ - $ 167,915 Interdepartmental revenues 273 4,811 10,173 - - ( 15,257) - Total operating revenues 100,882 72,081 10,209 - - ( 15,257) 167,915 Equity in earnings of investments - - - 2,444 - - 2,444 Net income (loss) 18,024 10,556 5,194 1,778 ( 619) - 34,933 Three Months Ended March 31, 2020 Operating revenues from external customers $ 92,990 $ 56,845 $ 38 $ - $ - $ - $ 149,873 Interdepartmental revenues 191 3,451 10,056 - - ( 13,698) - Total operating revenues 93,181 60,296 10,094 - - ( 13,698) 149,873 Equity in earnings of investments - - - 2,286 - - 2,286 Net income (loss) 11,463 8,034 5,060 1,663 ( 183) - 26,037 The following tables show segment information for MGE's operations for the indicated periods: (In thousands) MGE Electric Gas Nonregulated Energy Consolidation/ Elimination Consolidated Total Three Months Ended March 31, 2021 Operating revenues from external customers $ 100,609 $ 67,270 $ 36 $ - $ 167,915 Interdepartmental revenues 273 4,811 10,173 ( 15,257) - Total operating revenues 100,882 72,081 10,209 ( 15,257) 167,915 Net income attributable to MGE 18,024 10,556 5,194 ( 5,501) 28,273 Three Months Ended March 31, 2020 Operating revenues from external customers $ 92,990 $ 56,845 $ 38 $ - $ 149,873 Interdepartmental revenues 191 3,451 10,056 ( 13,698) - Total operating revenues 93,181 60,296 10,094 ( 13,698) 149,873 Net income attributable to MGE 11,463 8,034 5,060 ( 5,493) 19,064

Summary of Significant Accoun_3

Summary of Significant Accounting Principles (Details-1) - USD ($)	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents	$ 40,239,000	$ 44,738,000
Restricted cash	467,000	644,000
Receivable - margin account	796,000	1,657,000
Cash, cash equivalents, and restricted cash	41,502,000	47,039,000	$ 19,794,000	$ 25,814,000
MGE [Member]
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents	6,709,000	4,103,000
Restricted cash	467,000	644,000
Receivable - margin account	796,000	1,657,000
Cash, cash equivalents, and restricted cash	$ 7,972,000	$ 6,404,000	$ 5,664,000	$ 5,529,000

Investment in ATC and ATC Hol_3

Investment in ATC and ATC Holdco (Details-1) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Schedule Of Equity Method Investments [Line Items]
Equity earnings from investment	$ 2,444	$ 2,266
Dividends from investments	1,967	2,700
Capital contributions to investments	670	1,643
MGE Transco [Member] | ATC [Member]
Schedule Of Equity Method Investments [Line Items]
Equity earnings from investment	2,420	2,266
Dividends from investments	1,967	2,391
Capital contributions to investments	$ 0	$ 178

Investment in ATC and ATC Hol_4

Investment in ATC and ATC Holdco (Details-2) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
ATC [Member]
Schedule Of Equity Method Investments [Line Items]
Operating revenues	$ 188,694	$ 186,801
Operating expenses	(95,104)	(95,211)
Other income, net	378	375
Interest expense, net	(28,871)	(28,888)
Earnings before members' income taxes	65,097	63,077
ATC [Member]
Related Party Transaction [Line Items]
Related party expenses	8,000	$ 7,700
Due from related parties	$ 3,000		$ 2,600

Taxes (Details)

Taxes (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Reconciliation of tax provision to statutory federal income tax rate [Abstract]
Statutory federal income tax rate		21.00%	21.00%
State income taxes, net of federal benefit		6.30%	6.30%
Amortized investment tax credits		(1.60%)	(0.10%)
Credit for electricity from wind energy		(7.10%)	(6.90%)
AFUDC equity, net		(0.60%)	(1.60%)
Amortization of utility excess deferred tax - tax reform	[1]	(16.70%)	(2.60%)
Other, net, individually significant		0.00%	0.00%
Effective income tax rate		1.30%	16.10%
Excess Deferred Taxes, Tax Cuts And Jobs Act [Member]
Effects Of The Tax Cuts And Jobs Act [Abstract]
Excess deferred tax - Income statement effect		$ 0.7	$ 0.7
Return of unprotected excess deferred taxes		$ 3.3
MGE [Member]
Reconciliation of tax provision to statutory federal income tax rate [Abstract]
Statutory federal income tax rate		21.00%	21.00%
State income taxes, net of federal benefit		6.30%	6.30%
Amortized investment tax credits		(1.80%)	(0.10%)
Credit for electricity from wind energy		(7.80%)	(7.50%)
AFUDC equity, net		(0.60%)	(1.70%)
Amortization of utility excess deferred tax - tax reform	[1]	(18.30%)	(2.80%)
Other, net, individually significant		(0.10%)	(0.10%)
Effective income tax rate		(1.30%)	15.10%
[1]	Included are impacts of the 2017 Tax Act for the regulated utility for excess deferred taxes recognized using a normalization method of accounting in recognition of IRS rules that restrict the rate at which the excess deferred taxes may be returned to utility customers. For the three months ended March 31, 2021 and 2020, MGE recognized $ 0.7 million. Included in the 2021 rate settlement was a one-time return to customers of the electric portion of excess deferred taxes related to the 2017 Tax Act not restricted by IRS normalization rules. For the three months ended March 31, 2021, MGE recognized $ 3.3 million.

Pension and Other Postretirem_3

Pension and Other Postretirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan Deferred Pension And Other Postretirement Benefit Plan Costs Recovered [Abstract]
Deferred (recognized) pension and OPEB costs	$ (3,400)	$ (400)
Pension Benefits [Member]
Components of net periodic benefit cost:
Service cost	1,422	1,316
Interest cost	2,272	3,023
Expected return on assets	(7,375)	(6,811)
Amortization of:
Prior service credit	(31)	(31)
Actuarial loss	1,580	1,286
Net periodic benefit (credit) cost	(2,132)	(1,217)
Postretirement Benefits [Member]
Components of net periodic benefit cost:
Service cost	351	311
Interest cost	384	573
Expected return on assets	(817)	(790)
Amortization of:
Transition obligation	1	1
Prior service credit	(380)	(667)
Actuarial loss	109	70
Net periodic benefit (credit) cost	$ (352)	$ (502)

Equity and Financing Arrangem_2

Equity and Financing Arrangements (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Common Stock [Abstract]
Common stock issued during period under the stock plan	0	0
Dilutive Shares Calculation [Abstract]
Shares included in diluted earnings per share	1,543

Share Based Compensation (Detai

Share Based Compensation (Details) - USD ($) $ in Millions	Feb. 19, 2021	Jan. 31, 2021	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense (benefit)			$ 0.7	$ (0.6)
2021 Long Term Incentive Plan [Member] | Performance Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted during period (in units)	10,187
2021 Long Term Incentive Plan [Member] | Restricted Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted during period (in units)	16,267
2006 Performance Unit Plan and 2013 Director Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash payments distributed related to awards previously granted and now payable		$ 1.9

Commitments and Contingencies (

Commitments and Contingencies (Details-1) $ in Millions	Mar. 31, 2021USD ($)
Columbia Units [Member]
Public Utilities, General Disclosures [Line Items]
Projected Costs For Environmental Regulation	$ 4
Elm Road Units [Member]
Public Utilities, General Disclosures [Line Items]
Projected Costs For Environmental Regulation	$ 4

Rate Matters (Details)

Rate Matters (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fuel Rules [Abstract]
Deferred fuel rules monitored costs	$ 0.5				$ 3.2	$ 1.5
Rate Matters For Future Periods [Member] | Subsequent Event [Member]
Rate Proceedings [Abstract]
Proposed return on equity, percentage			9.80%
Proposed equity capital structure, percentage			55.60%
PSCW [Member] | MGE [Member]
Rate Proceedings [Abstract]
Authorized return on equity, percentage	9.80%				9.80%	9.80%
Approved equity capital structure, percentage	55.80%				56.10%	56.60%
Fuel Rules [Abstract]
Fuel rules, bandwidth	1.00%				2.00%
Fuel rules, electric fuel deferred costs upper threshold	101.00%
Fuel rules, electric fuel deferred costs lower threshold	99.00%
Electric Rate Proceeding [Member] | Rate Matters For Future Periods [Member] | Subsequent Event [Member]
Rate Proceedings [Abstract]
Proposed rate increase (decrease), percentage			5.90%
Electric Rate Proceeding [Member] | PSCW [Member] | MGE [Member]
Rate Proceedings [Abstract]
Authorized rate increase (decrease), percentage	0.00%				(0.84%)	(2.24%)
Authorized rate increase (decrease), amount					$ (3.4)	$ (9.2)
Electric Rate Proceeding [Member] | PSCW [Member] | Rate Matters For Future Periods [Member] | MGE [Member]
Effects Of The Tax Cuts And Jobs Act [Abstract]
Return of unprotected excess deferred taxes				$ 18.2
Gas Rate Proceeding [Member] | Rate Matters For Future Periods [Member] | Subsequent Event [Member]
Rate Proceedings [Abstract]
Proposed rate increase (decrease), percentage		1.65%	3.00%
Gas Rate Proceeding [Member] | PSCW [Member] | MGE [Member]
Rate Proceedings [Abstract]
Authorized rate increase (decrease), percentage	4.00%				1.46%	1.06%
Authorized rate increase (decrease), amount					$ 2.4	$ 1.7

Derivative and Hedging Instru_3

Derivative and Hedging Instruments (Details-1)		3 Months Ended	12 Months Ended
		Mar. 31, 2021USD ($)DthMWhMW	Dec. 31, 2020USD ($)DthMWhMW	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Derivative fair values [Abstract]
Collateral posted against derivative positions		$ 0	$ 0
Other Current Assets [Member]
Derivative fair values [Abstract]
Derivative fair value, net		173,000	1,162,000	$ 430,000	$ 1,100,000
Commodity Contracts And Financial Transimission Rights [Member]
Derivative fair values [Abstract]
Derivative fair value, net		$ 500,000	$ 200,000
Commodity Derivative Contracts [Member]
Gross Notional Volume of Open Derivatives
Notional amount, energy measure (in MWh) | MWh		277,400	259,080
Notional amount, decatherm measure (in Dth) | Dth		2,190,000	6,030,000
Derivative fair values [Abstract]
Asset Derivatives, fair value, gross basis		$ 683,000	$ 806,000
Liability Derivatives, fair value, gross basis		190,000	632,000
Collateral posted against derivative positions		0	0
Collateral posted against derivative positions		0	0
Commodity Derivative Contracts [Member] | Other Current Assets [Member]
Derivative fair values [Abstract]
Asset Derivatives, fair value, gross basis	[1]	653,000	617,000
Liability Derivatives, fair value, gross basis	[1]	174,000	593,000
Commodity Derivative Contracts [Member] | Other Deferred Charges [Member]
Derivative fair values [Abstract]
Asset Derivatives, fair value, gross basis	[1]	30,000	189,000
Liability Derivatives, fair value, gross basis	[1]	16,000	39,000
Commodity Derivative Contracts [Member] | Cash Flow Hedging [Member]
Derivative fair values [Abstract]
Collateral posted against derivative positions		$ 0	$ 0
Energy Related Commodity Contract [Member] | Cash Flow Hedging [Member]
Derivatives Fair Value [Line Items]
Maximum term of derivative hedging contract		4 years
Financial Transmission Rights [Member]
Gross Notional Volume of Open Derivatives
Notional amount, power measure (in MW) | MW		1,152	2,869
Derivative fair values [Abstract]
Asset Derivatives, fair value, gross basis		$ 38,000
Liability Derivatives, fair value, gross basis			$ 23,000
Collateral posted against derivative positions			0
Collateral posted against derivative positions		0
Financial Transmission Rights [Member] | Other Current Assets [Member]
Derivative fair values [Abstract]
Asset Derivatives, fair value, gross basis		38,000
Liability Derivatives, fair value, gross basis		$ 0
Financial Transmission Rights [Member] | Other Current Liabilities [Member]
Derivative fair values [Abstract]
Asset Derivatives, fair value, gross basis			0
Liability Derivatives, fair value, gross basis			$ 23,000
PPA [Member]
Gross Notional Volume of Open Derivatives
Notional amount, power measure (in MW) | MW		700	850
Derivative fair values [Abstract]
Derivative fair value, net		$ (11,600,000)	$ (14,100,000)
Liability Derivatives, fair value, gross basis		11,590,000	14,140,000
Collateral posted against derivative positions		0	0
PPA [Member] | Derivative Liability (Current) [Member]
Derivative fair values [Abstract]
Liability Derivatives, fair value, gross basis		9,790,000	10,160,000
PPA [Member] | Derivative Liability (Long-term) [Member]
Derivative fair values [Abstract]
Liability Derivatives, fair value, gross basis		$ 1,800,000	$ 3,980,000
[1]	No collateral was posted against derivative positions as of March 31, 2021, and December 31, 2020

Derivative and Hedging Instru_4

Derivative and Hedging Instruments (Details-2) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Commodity Derivative Contracts [Member]
Offsetting Assets [Line Items]
Gross amounts	$ 683	$ 806
Gross amounts offset in balance sheet	(190)	(632)
Collateral posted against derivative positions	0	0
Net amount presented in balance sheet	493	$ 174
Financial Transmission Rights [Member]
Offsetting Assets [Line Items]
Gross amounts	38
Gross amounts offset in balance sheet	0
Collateral posted against derivative positions	0
Net amount presented in balance sheet	$ 38

Derivative and Hedging Instru_5

Derivative and Hedging Instruments (Details-3) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Offsetting Liabilities [Line Items]
Collateral posted against derivative positions	$ 0	$ 0
Commodity Derivative Contracts [Member]
Offsetting Liabilities [Line Items]
Gross amounts	190,000	632,000
Gross amounts offset in balance sheet	(190,000)	(632,000)
Collateral posted against derivative positions	0	0
Net amount presented in balance sheet	0	0
Financial Transmission Rights [Member]
Offsetting Liabilities [Line Items]
Gross amounts		23,000
Gross amounts offset in balance sheet		0
Collateral posted against derivative positions		0
Net amount presented in balance sheet		23,000
Purchased Power Agreement [Member]
Offsetting Liabilities [Line Items]
Gross amounts	11,590,000	14,140,000
Gross amounts offset in balance sheet	0	0
Collateral posted against derivative positions	0	0
Net amount presented in balance sheet	$ 11,590,000	$ 14,140,000

Derivative and Hedging Instru_6

Derivative and Hedging Instruments (Details-4) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Current and Long-Term Regulatory Asset [Member]
Change In Derivative Fair Value [Roll Forward]
Beginning balance,	$ 13,989	$ 26,875
Unrealized (gain) loss	(3,588)	(689)
Realized (loss) gain reclassified to a deferred account	(50)	(1,063)
Realized (loss) gain reclassified to income statement	708	204
Ending balance,	11,059	25,327
Other Current Assets [Member]
Change In Derivative Fair Value [Roll Forward]
Beginning balance,	1,162	1,100
Unrealized (gain) loss	0	0
Realized (loss) gain reclassified to a deferred account	50	1,063
Realized (loss) gain reclassified to income statement	(1,039)	(1,733)
Ending balance,	$ 173	$ 430

Derivative and Hedging Instru_7

Derivative and Hedging Instruments (Details-5)	3 Months Ended
	Mar. 31, 2021USD ($)counterparty	Mar. 31, 2020USD ($)	Dec. 31, 2020USD ($)
Counterparties in net liability position or default [Abstract]
Derivative, net liability position of counterparties	$ 0		$ 0
Number of counterparties in default | counterparty	0
Commodity Derivative Contracts [Member] | Fuel For Electric Generation Purchased Power [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	$ (195,000)	$ 680,000
Commodity Derivative Contracts [Member] | Cost Of Gas Sold Expense [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	1,022,000	1,607,000
Financial Transmission Rights [Member] | Fuel For Electric Generation Purchased Power [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	(256,000)	(65,000)
Financial Transmission Rights [Member] | Cost Of Gas Sold Expense [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	0	0
Purchased Power Agreement [Member]
Derivative collateral required to be posted for PPA [Abstract]
Minimum collateral that may be required to be posted	20,000,000
Maximum collateral that may be required to be posted	40,000,000
Collateral posted	0
Purchased Power Agreement [Member] | Fuel For Electric Generation Purchased Power [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	(240,000)	(693,000)
Purchased Power Agreement [Member] | Cost Of Gas Sold Expense [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	$ 0	$ 0

Fair Value of Financial Instr_3

Fair Value of Financial Instruments (Details-1) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020
Fair Value Measurement [Domain]
Liabilities:
Unamortized discount and debt issuance costs, net		$ 4,000	$ 4,100
Carrying Amount [Member]
Assets:
Cash and cash equivalents		40,239	44,738
Liabilities:
Short-term debt - commercial paper		54,000	52,500
Long-term debt	[1]	527,038	528,220
Fair Value [Member]
Assets:
Cash and cash equivalents		40,239	44,738
Liabilities:
Short-term debt - commercial paper		54,000	52,500
Long-term debt	[1]	590,748	639,271
MGE [Member] | Fair Value Measurement [Domain]
Liabilities:
Unamortized discount and debt issuance costs, net		4,000	4,100
MGE [Member] | Carrying Amount [Member]
Assets:
Cash and cash equivalents		6,709	4,103
Liabilities:
Short-term debt - commercial paper		54,000	52,500
Long-term debt	[1]	527,038	528,220
MGE [Member] | Fair Value [Member]
Assets:
Cash and cash equivalents		6,709	4,103
Liabilities:
Short-term debt - commercial paper		54,000	52,500
Long-term debt	[1]	$ 590,748	$ 639,271
[1]	Includes long-term debt due within one year. Excludes debt issuance costs and unamortized discount of $ 4.0 million and $ 4.1 million as of March 31, 2021, and December 31, 2020, respectively.

Fair Value of Financial Instr_4

Fair Value of Financial Instruments (Details-2) - USD ($)		Mar. 31, 2021	Dec. 31, 2020
Liabilities:
Collateral posted against derivative positions		$ 0	$ 0
Recurring [Member]
Assets:
Derivatives	[1]	721,000	806,000
Total Assets		2,195,000	2,556,000
Liabilities:
Derivatives	[1]	11,780,000	14,795,000
Deferred compensation		3,581,000	3,509,000
Total liabilities		15,361,000	18,304,000
Recurring [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities		1,474,000	1,750,000
Recurring [Member] | Level 1 [Member]
Assets:
Derivatives	[1]	423,000	436,000
Total Assets		1,897,000	2,186,000
Liabilities:
Derivatives	[1]	115,000	370,000
Deferred compensation		0	0
Total liabilities		115,000	370,000
Recurring [Member] | Level 1 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities		1,474,000	1,750,000
Recurring [Member] | Level 2 [Member]
Assets:
Derivatives	[1]	0	0
Total Assets		0	0
Liabilities:
Derivatives	[1]	0	0
Deferred compensation		3,581,000	3,509,000
Total liabilities		3,581,000	3,509,000
Recurring [Member] | Level 2 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities		0	0
Recurring [Member] | Level 3 [Member]
Assets:
Derivatives	[1]	298,000	370,000
Total Assets		298,000	370,000
Liabilities:
Derivatives	[1]	11,665,000	14,425,000
Deferred compensation		0	0
Total liabilities		11,665,000	14,425,000
Recurring [Member] | Level 3 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities		0	0
MGE [Member] | Recurring [Member]
Assets:
Derivatives	[1]	721,000	806,000
Total Assets		1,152,000	1,409,000
Liabilities:
Derivatives	[1]	11,780,000	14,795,000
Deferred compensation		3,581,000	3,509,000
Total liabilities		15,361,000	18,304,000
MGE [Member] | Recurring [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities		431,000	603,000
MGE [Member] | Recurring [Member] | Level 1 [Member]
Assets:
Derivatives	[1]	423,000	436,000
Total Assets		854,000	1,039,000
Liabilities:
Derivatives	[1]	115,000	370,000
Deferred compensation		0	0
Total liabilities		115,000	370,000
MGE [Member] | Recurring [Member] | Level 1 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities		431,000	603,000
MGE [Member] | Recurring [Member] | Level 2 [Member]
Assets:
Derivatives	[1]	0	0
Total Assets		0	0
Liabilities:
Derivatives	[1]	0	0
Deferred compensation		3,581,000	3,509,000
Total liabilities		3,581,000	3,509,000
MGE [Member] | Recurring [Member] | Level 2 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities		0	0
MGE [Member] | Recurring [Member] | Level 3 [Member]
Assets:
Derivatives	[1]	298,000	370,000
Total Assets		298,000	370,000
Liabilities:
Derivatives	[1]	11,665,000	14,425,000
Deferred compensation		0	0
Total liabilities		11,665,000	14,425,000
MGE [Member] | Recurring [Member] | Level 3 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities		$ 0	$ 0
[1]	These amounts are shown gross. No collateral was posted against derivative positions with counterparties as of March 31, 2021, or December 31, 2020.

Fair Value of Financial Instr_5

Fair Value of Financial Instruments (Details-3)	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Basis adjustment:
Basis adjustment - on peak	94.40%	94.20%
Basis adjustment - off peak	95.00%	94.50%
US Treasury Bill Securities [Member]
Deferred compensation plan [Abstract]
Investment interest calculation, investment maturity period (26 weeks)	182 days
Investment interest calculation, monthly compounding rate	1.00%
Investment interest calculation, minimum annual rate compounded monthly	7.00%
Minimum [Member]
Counterparty fuel mix:
Internal generation	41.00%	46.00%
Purchased power	34.00%	35.00%
Maximum [Member]
Counterparty fuel mix:
Internal generation	66.00%	65.00%
Purchased power	59.00%	54.00%
Weighted Average [Member]
Counterparty fuel mix:
Internal generation	56.90%	56.50%
Purchased power	43.10%	43.50%

Fair Value of Financial Instr_6

Fair Value of Financial Instruments (Details-4) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance,		$ (14,055)	$ (26,456)
Realized and unrealized gains (losses):
Included in regulatory assets		2,688	810
Included in other comprehensive income		0	0
Included in earnings	[1]	307	(1,453)
Included in current assets		355	247
Purchases		5,884	5,015
Sales		0	0
Issuances		0	0
Settlements		(6,546)	(3,810)
Ending balance,		$ (11,367)	$ (25,647)
[1]	MGE's exchange-traded derivative contracts, over-the-counter party transactions, purchased power agreement, and FTRs are subject to regulatory deferral. These derivatives are therefore marked to fair value and are offset in the financial statements with a corresponding regulatory asset or liability.

Fair Value of Financial Instr_7

Fair Value of Financial Instruments (Details-5) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Total gains (losses) included in earnings attributed to the change in unrealized gains (losses) related to assets and liabilities	[1]	$ 0	$ 0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Included in earnings	[1]	307	(1,453)
Purchased Power Expense [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Included in earnings		702	(1,184)
Cost Of Gas Sold Expense [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Included in earnings		$ (395)	$ (269)
[1]	MGE's exchange-traded derivative contracts, over-the-counter party transactions, purchased power agreement, and FTRs are subject to regulatory deferral. These derivatives are therefore marked to fair value and are offset in the financial statements with a corresponding regulatory asset or liability.

Joint Plant Ownership (Details)

Joint Plant Ownership (Details) $ in Millions		3 Months Ended
		Mar. 31, 2021USD ($)MW	Mar. 31, 2020USD ($)
Badger Hollow I Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected Solar Farm Project Costs	[1]	$ 65
Public Utilities Property Plant And Equipment Construction Work In Progress	[1],[2]	$ 56.4
Badger Hollow I Units [Member] | Public Service Commission of Wisconsin [Member]
Allowance for Funds Used During Construction
Authorized AFUDC rate - Signficiant projects (100%)		100.00%
Badger Hollow I Units [Member] | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest	[1]	33.00%
Jointly owned utility plant, plant capacity (in MW) | MW	[1]	50
Badger Hollow II Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected Solar Farm Project Costs	[1]	$ 65
Public Utilities Property Plant And Equipment Construction Work In Progress	[1],[2]	$ 5.3
Badger Hollow II Units [Member] | Public Service Commission of Wisconsin [Member]
Allowance for Funds Used During Construction
Authorized AFUDC rate - Signficiant projects (100%)		100.00%
Badger Hollow II Units [Member] | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest	[1]	33.00%
Jointly owned utility plant, plant capacity (in MW) | MW	[1]	50
Badger Hollow I and II [Member]
Allowance for Funds Used During Construction
AFUDC		$ 1.1	$ 0.4
[1]	The Badger Hollow I and Badger Hollow II solar farms are located in southwestern Wisconsin in Iowa County, near the villages of Montfort and Cobb.
[2]	Excluding AFUDC.

Revenue (Details-1)

Revenue (Details-1) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Total Operating Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	$ 167,915	$ 149,873
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	100,609	92,990
Electric [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	36,694	33,428
Electric [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	47,883	47,634
Electric [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	3,001	2,800
Electric [Member] | Other-retail/municipal
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	8,170	8,204
Electric [Member] | Total Retail [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	95,748	92,066
Electric [Member] | Sales To The Market [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	4,639	482
Electric [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	222	442
Gas [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	67,270	56,845
Gas [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	39,758	33,487
Gas [Member] | Commercial/Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	25,507	21,471
Gas [Member] | Total Retail [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	65,265	54,958
Gas [Member] | Gas Transportation [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	2,002	1,794
Gas [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	3	93
Non Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	$ 36	$ 38

Segment Information (Details)

Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Operating revenues	$ 167,915	$ 149,873
Equity in earnings of investment	2,444	2,266
Net Income	34,933	26,037
Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	100,609	92,990
Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	67,270	56,845
Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	36	38
Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0
All Others [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	167,915	149,873
Equity in earnings of investment	2,444	2,286
Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	100,882	93,181
Equity in earnings of investment	0	0
Net Income	18,024	11,463
Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	72,081	60,296
Equity in earnings of investment	0	0
Net Income	10,556	8,034
Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	10,209	10,094
Equity in earnings of investment	0	0
Net Income	5,194	5,060
Operating Segments [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0
Equity in earnings of investment	2,444	2,286
Net Income	1,778	1,663
Operating Segments [Member] | All Others [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0
Equity in earnings of investment	0	0
Net Income	(619)	(183)
Consolidation Elimination Entries [Member]
Segment Reporting Information [Line Items]
Operating revenues	(15,257)	(13,698)
Equity in earnings of investment	0	0
Net Income	0	0
Consolidation Elimination Entries [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	273	191
Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	4,811	3,451
Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	10,173	10,056
Consolidation Elimination Entries [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0
Consolidation Elimination Entries [Member] | All Others [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0
MGE [Member]
Segment Reporting Information [Line Items]
Operating revenues	167,915	149,873
Net Income	28,273	19,064
MGE [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	100,609	92,990
MGE [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	67,270	56,845
MGE [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	36	38
MGE [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	167,915	149,873
Net Income	28,273	19,064
MGE [Member] | Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	100,882	93,181
Net Income	18,024	11,463
MGE [Member] | Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	72,081	60,296
Net Income	10,556	8,034
MGE [Member] | Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	10,209	10,094
Net Income	5,194	5,060
MGE [Member] | Consolidation Elimination Entries [Member]
Segment Reporting Information [Line Items]
Operating revenues	(15,257)	(13,698)
Net Income	(5,501)	(5,493)
MGE [Member] | Consolidation Elimination Entries [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	273	191
MGE [Member] | Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	4,811	3,451
MGE [Member] | Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	$ 10,173	$ 10,056