MGE Energy (MGEE) 10-Q 7 May 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015
Document And Entity Information [Line Items]
Entity Registrant Name	MGE Energy Inc
Entity Central Index Key	1161728
Document Type	10-Q
Document Period End Date	31-Mar-15
Amendment Flag	FALSE
Trading Symbol	MGEE
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	-19
Entity Well known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock Shares Outstanding	34,668,370
MGE [Member]
Document And Entity Information [Line Items]
Entity Registrant Name	Madison Gas and Electric Company
Entity Central Index Key	61339
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock Shares Outstanding	17,347,894

MGE_Energy_Inc_Consolidated_St

MGE Energy Inc Consolidated Statements of Income (Unaudited) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Operating Revenues:
Regulated electric revenues	$98,240	$98,852
Regulated gas revenues	69,928	110,713
Nonregulated revenues	1,966	680
Total Operating Revenues	170,134	210,245
Operating Expenses:
Fuel for electric generation	11,892	14,132
Purchased power	22,865	18,555
Cost of gas sold	46,919	78,508
Other operations and maintenance	40,674	40,472
Depreciation and amortization	10,849	9,746
Other general taxes	5,084	4,861
Total Operating Expenses	138,283	166,274
Operating Income	31,851	43,971
Other income, net	2,105	4,552
Interest expense, net	-5,091	-4,541
Income before income taxes	28,865	43,982
Income tax provision	-10,587	-16,265
Net Income (Loss)	$18,278	$27,717
Earnings Per Share of Common Stock (basic and diluted)	$0.53	$0.80
Dividends per share of common stock	$0.28	$0.27
Weighted Average Shares Outstanding (basic and diluted)	34,668	34,668

Madison_Gas_and_Electric_Compa

Madison Gas and Electric Company Consolidated Statements of Income (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Operating Revenues:
Regulated electric revenues	$98,240		$98,852
Regulated gas revenues	69,928		110,713
Nonregulated revenues	1,966		680
Total Operating Revenues	170,134		210,245
Operating Expenses:
Fuel for electric generation	11,892		14,132
Purchased power	22,865		18,555
Cost of gas sold	46,919		78,508
Other operations and maintenance	40,674		40,472
Depreciation and amortization	10,849		9,746
Other general taxes	5,084		4,861
Income tax provision	10,587		16,265
Total Operating Expenses	138,283		166,274
Operating Income	31,851		43,971
Other Income and Deductions:
Equity in earnings in ATC	1,881		2,481
Total Other Income and Deductions	2,105		4,552
Interest Expense:
Net Interest Expense	5,091		4,541
Net Income (Loss)	18,278		27,717
MGE [Member]
Operating Revenues:
Regulated electric revenues	98,245		98,858
Regulated gas revenues	69,933		110,718
Nonregulated revenues	1,966		680
Total Operating Revenues	170,144		210,256
Operating Expenses:
Fuel for electric generation	11,894		14,134
Purchased power	22,868		18,558
Cost of gas sold	46,923		78,513
Other operations and maintenance	40,472		40,317
Depreciation and amortization	10,837		9,734
Other general taxes	5,084		4,861
Income tax provision	9,776		14,924
Total Operating Expenses	147,854		181,041
Operating Income	22,290	[1]	29,215	[1]
Other Income and Deductions:
AFUDC - equity funds	128		1,950
Equity in earnings in ATC	1,881		2,481
Income tax provision	-808		-1,264
Other expense, net	-39		-158
Total Other Income and Deductions	1,162	[1]	3,009	[1]
Income before interest expense	23,452		32,224
Interest Expense:
Interest on long-term debt	5,151		5,249
Other interest, net	32		-25
AFUDC - borrowed funds	-42		-643
Net Interest Expense	5,141		4,581
Net Income Including Noncontrolling Interest	18,311		27,643
Less Net Income Attributable to Noncontrolling Interest, net of tax	-6,553		-6,510
Net Income (Loss)	$11,758		$21,133
[1]	*Amounts are shown net of the related tax expense, consistent with the presentation on the consolidated MGE Income Statement.

MGE_Energy_Inc_Consolidated_St1

MGE Energy Inc Consolidated Statements of Comprehensive Income (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Comprehensive Income [Abstract]
Net Income	$18,278	$27,717
Other comprehensive income (loss), net of tax:
Unrealized (loss) gain on available-for-sale securities, net of tax	-85	7
Comprehensive Income	$18,193	$27,724

Madison_Gas_and_Electric_Compa1

Madison Gas and Electric Company Consolidated Statements of Comprehensive Income (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Other comprehensive income/(loss), net of tax:
Unrealized (loss) gain on available-for-sale securities, net of tax	($85)	$7
Comprehensive Income	18,193	27,724
MGE [Member]
Net Income	18,311	27,643
Other comprehensive income/(loss), net of tax:
Unrealized (loss) gain on available-for-sale securities, net of tax	-82	18
Total comprehensive income including noncontrolling interest	18,229	27,661
Less: Comprehensive income attributable to Noncontrolling Interest, net of tax	-6,553	-6,510
Comprehensive Income	$11,676	$21,151

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (Unaudited) (Parantheticals) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Unrealized gain (loss) on available-for-sale securities, tax (benefit) expense	($57)	$5
MGE [Member]
Unrealized gain (loss) on available-for-sale securities, tax (benefit) expense	($55)	$12

MGE_Energy_Inc_Consolidated_St2

MGE Energy Inc Consolidated Statements of Cash Flows (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Operating Activities:
Net Income	$18,278	$27,717
Items not affecting cash:
Depreciation and amortization	10,849	9,746
Deferred income taxes	3,723	-877
Provision for doubtful receivables	97	743
Employee benefit plan expenses	792	-332
Equity earnings in ATC	-1,881	-2,481
Other items	-658	-679
Changes in working capital items:
Decrease in current assets	17,985	3,283
(Decrease) increase in current liabilities	-11,091	19,604
Dividend income from ATC	1,420	1,917
Cash contributions to pension and other postretirement plans	-10,809	-818
Other noncurrent items, net	5,935	547
Cash Provided by Operating Activities	34,640	58,370
Investing Activities:
Capital expenditures	-11,533	-21,800
Capital contributions to investments	-280	-693
Other	-48	-682
Cash Used for Investing Activities	-11,861	-23,175
Financing Activities:
Cash dividends paid on common stock	-9,794	-9,420
Repayment of long-term debt	-1,037	-1,019
Repayment of short-term debt	-7,000	0
Other	0	-80
Cash Used for Financing Activities	-17,831	-10,519
Change in cash and cash equivalents	4,948	24,676
Cash and cash equivalents at beginning of period	65,755	68,813
Cash and Cash Equivalents at End of Period	$70,703	$93,489

Madison_Gas_and_Electric_Compa2

Madison Gas and Electric Company Consolidated Statements of Cash Flows (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Items not affecting cash:
Depreciation and amortization	$10,849	$9,746
Deferred income taxes	3,723	-877
Provision for doubtful receivables	97	743
Employee benefit plan expenses	792	-332
Equity earnings in ATC	-1,881	-2,481
Other items	-658	-679
Changes in working capital items:
Decrease in current assets	17,985	3,283
(Decrease) increase in current liabilities	-11,091	19,604
Dividend income from ATC	1,420	1,917
Cash contributions to pension and other postretirement plans	-10,809	-818
Other noncurrent items, net	5,935	547
Cash Provided by Operating Activities	34,640	58,370
Investing Activities:
Capital expenditures	-11,533	-21,800
Capital contributions to investments	-280	-693
Other	-48	-682
Cash Used for Investing Activities	-11,861	-23,175
Financing Activities:
Repayment of long-term debt	-1,037	-1,019
Repayment of short-term debt	-7,000	0
Other	0	-80
Cash Used for Financing Activities	-17,831	-10,519
Change in cash and cash equivalents	4,948	24,676
Cash and cash equivalents at beginning of period	65,755	68,813
Cash and Cash Equivalents at End of Period	70,703	93,489
MGE [Member]
Operating Activities:
Net Income	18,311	27,643
Items not affecting cash:
Depreciation and amortization	10,837	9,734
Deferred income taxes	2,391	-1,141
Provision for doubtful receivables	97	743
Employee benefit plan expenses	792	-332
Equity earnings in ATC	-1,881	-2,481
Other items	-526	-546
Changes in working capital items:
Decrease in current assets	18,825	7,817
(Decrease) increase in current liabilities	-8,859	17,488
Dividend income from ATC	1,420	1,917
Cash contributions to pension and other postretirement plans	-10,809	-818
Other noncurrent items, net	5,901	521
Cash Provided by Operating Activities	36,499	60,545
Investing Activities:
Capital expenditures	-11,533	-21,800
Capital contributions to investments	-178	-533
Other	-17	-637
Cash Used for Investing Activities	-11,728	-22,970
Financing Activities:
Cash dividends paid to parent by MGE	0	-7,000
Distributions to parent from noncontrolling interest	-6,818	-6,909
Equity contribution received by noncontrolling interest	2,678	533
Repayment of long-term debt	-1,037	-1,019
Repayment of short-term debt	-7,000	0
Cash Used for Financing Activities	-12,177	-14,395
Change in cash and cash equivalents	12,594	23,180
Cash and cash equivalents at beginning of period	4,562	14,808
Cash and Cash Equivalents at End of Period	$17,156	$37,988

Consolidated_Balance_Sheets_Un

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

Consolidated_Balance_Sheets_Un1

Consolidated Balance Sheets (Unaudited) (Parentheticals) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Receivables, Net
Reserve for uncollectible accounts receivable	$3,972	$4,329
Reserve for uncollectible other accounts receivable	401	420
MGE [Member]
Receivables, Net
Reserve for uncollectible accounts receivable	3,972	4,329
Reserve for uncollectible other accounts receivable	$401	$420

MGE_Energy_Inc_Consolidated_St3

MGE Energy Inc Consolidated Statements of Common Equity (Unaudited) (USD $)	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]
In Thousands, unless otherwise specified
Beginning balance, value at Dec. 31, 2013	$617,510	$34,668	$316,268	$266,197	$377
Beginning balance, shares at Dec. 31, 2013		34,668
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income	27,717			27,717
Other comprehensive income (loss)	7				7
Common stock dividends declared	-9,420			-9,420
Cash in lieu of fractional shares related to stock split	-80			-80
Ending balance, value at Mar. 31, 2014	635,734	34,668	316,268	284,414	384
Ending balance, shares at Mar. 31, 2014		34,668
Beginning balance, value at Dec. 31, 2014	659,401	34,668	316,268	308,007	458
Beginning balance, shares at Dec. 31, 2014		34,668
Beginning balance, value - Adjusted at Dec. 31, 2014	659,259			307,865
Cumulative effect of new accounting principle (See Footnote 4) at Dec. 31, 2014	-142			-142
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income	18,278			18,278
Other comprehensive income (loss)	-85				-85
Common stock dividends declared	-9,794			-9,794
Ending balance, value at Mar. 31, 2015	$667,658	$34,668	$316,268	$316,349	$373
Ending balance, shares at Mar. 31, 2015		34,668

Madison_Gas_and_Electric_Compa3

Madison Gas and Electric Company Consolidated Statements of Common Equity (Unaudited) (USD $)	Total	MGE [Member]	Common Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss)/Income [Member]	Accumulated Other Comprehensive (Loss)/Income [Member]	Noncontrolling Interest [Member]
In Thousands, unless otherwise specified	USD ($)	USD ($)		MGE [Member]	MGE [Member]	USD ($)	MGE [Member]	USD ($)	MGE [Member]	MGE [Member]
				USD ($)	USD ($)		USD ($)		USD ($)	USD ($)
Beginning balance, value at Dec. 31, 2013		$576,454		$17,348	$192,417		$247,534		$192	$118,963
Beginning balance, shares at Dec. 31, 2013			34,668	17,348
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income		27,643					21,133			6,510
Other comprehensive income (loss)	7	18						7	18
Cash dividends paid to parent by MGE		-7,000					-7,000
Equity contribution received by noncontrolling interest		533								533
Distributions to parent from noncontrolling interest		-6,909								-6,909
Ending balance, value at Mar. 31, 2014		590,739		17,348	192,417		261,667		210	119,097
Ending balance, shares at Mar. 31, 2014			34,668	17,348
Beginning balance, value - Adjusted at Dec. 31, 2014		612,118					276,520
Beginning balance, value at Dec. 31, 2014		612,260		17,348	192,417		276,662		144	125,689
Beginning balance, shares at Dec. 31, 2014			34,668	17,348
Cumulative effect of new accounting principle (See Footnote 4) at Dec. 31, 2014	-142	-142				-142	-142
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income		18,311					11,758			6,553
Other comprehensive income (loss)	-85	-82						-85	-82
Equity contribution received by noncontrolling interest		2,678								2,678
Distributions to parent from noncontrolling interest		-6,818								-6,818
Ending balance, value at Mar. 31, 2015		$626,207		$17,348	$192,417		$288,278		$62	$128,102
Ending balance, shares at Mar. 31, 2015			34,668	17,348

Consolidated_Statements_of_Com1

Consolidated Statements of Common Equity (Unaudited) (Parentheticals) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Consolidated Statements of Common Equity
Dividends per share of common stock	$0.28	$0.27

Basis_of_Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation - MGE Energy and MGE.
	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 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 2 of Notes to Consolidated Financial Statements under Item 8, Financial Statements and Supplementary Data, of MGE Energy's and MGE's 2014 Annual Report on Form 10-K.
	The accompanying consolidated financial statements as of March 31, 2015, and for 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 MGE Energy's and MGE's 2014 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 52 through 101 of the 2014 Annual Report on Form 10-K.

Equity_and_Financing_Arrangeme

Equity and Financing Arrangements	3 Months Ended
	Mar. 31, 2015
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 Stock Plan. Those shares may be newly issued shares or shares that MGE Energy has purchased in the open market for resale to 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. For both the three months ended March 31, 2015 and 2014, MGE Energy did not issue any new shares of common stock under the Stock Plan.
	b. Dilutive Shares Calculation - MGE Energy.
	MGE Energy does not hold any dilutive securities.

Investment_in_ATC

Investment in ATC	3 Months Ended
	Mar. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Investment in ATC	Investment in ATC - 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, which is jointly owned by MGE Energy and MGE.
	MGE Transco has accounted for its investment in ATC under the equity method of accounting. For the three months ended March 31, 2015 and 2014, MGE Transco recorded the following:
				Three Months Ended
				March 31,
		(In thousands)		2015		2014
		Equity in earnings from investment in ATC	$	1,881	$	2,481
		Dividends received from ATC		1,420		1,917
		Capital contributions to ATC		178		533
	On April 30, 2015, MGE Transco made a $0.2 million capital contribution to ATC.
	MGE Transco's investment in ATC as of March 31, 2015 and December 31, 2014 was $68.3 million and $67.7 million, respectively.
	At March 31, 2015, MGE is the majority owner, and MGE Energy, the holding company, is the minority owner of MGE Transco. MGE Energy's proportionate share of the equity and net income of MGE Transco is classified within the MGE financial statements as noncontrolling interest.
	ATC's summarized financial data for the three months ended March 31, 2015 and 2014, is as follows:
				Three Months Ended
				March 31,
		(In thousands)		2015		2014
		Operating revenues	$	152,357	$	163,337
		Operating expenses		-79,951		-78,623
		Other income, net		62		388
		Interest expense, net		-24,483		-21,996
		Earnings before members' income taxes	$	47,985	$	63,106

Chattel_Paper_Agreements

Chattel Paper Agreements	3 Months Ended
	Mar. 31, 2015
Transfers and Servicing [Abstract]
Chattel Paper Agreements	Chattel Paper Agreements - MGE Energy and MGE.
	MGE makes available to qualifying customers a financing program for the purchase and installation of energy-related equipment that will provide more efficient use of utility service at the customer's property. The energy-related equipment installed at the customer sites is used to secure the customer loans. MGE is party to a chattel paper purchase agreement with a financial institution under which it can sell or finance an undivided interest with recourse, in up to $10.0 million of the financing program receivables, until July 31, 2015. The length of the MGE guarantee to the financial institution varies from one to ten years depending on the term of the underlying customer loan. The loan balances outstanding at March 31, 2015, approximate the fair value of the energy-related equipment acting as collateral. MGE accounts for these agreements as secured borrowings.
	Prior to authoritative guidance that became effective in 2015, these agreements were treated as off-balance sheet arrangements. Beginning January 1, 2015, these agreements are included as assets and liabilities in the consolidated balance sheet. As of March 31, 2015, assets (other accounts receivable and other deferred assets) and liabilities (accounts payable and other deferred liabilities) increased approximately $4.3 million as a cumulative result of the guidance. In addition, the cumulative effect of this guidance resulted in a $0.1 million reduction in retained earnings.
	As of March 31, 2015, the remaining contractual maturities of the chattel paper agreements were as follows:
		(In thousands)		2015		2016		2017		2018		Thereafter		Total
		Repurchase-to-Maturity Transactions:
		Loans	$	383	$	950	$	552	$	540	$	1,841	$	4,266

Taxes

Taxes	3 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Taxes	Taxes - MGE Energy and MGE.
	Effective Tax Rate.
	MGE Energy's effective income tax rate for the three months ended March 31, 2015 and 2014, was 36.7% and 37.0%, respectively. MGE's effective income tax rate for the three months ended March 31, 2015 and 2014, was 36.6% and 36.9%, respectively. The decrease in the effective tax rate is due in part to a higher estimated domestic manufacturing deduction offset by lower AFUDC equity earnings in 2015.

Pension_and_Other_Postretireme

Pension and Other Postretirement Plans	3 Months Ended
	Mar. 31, 2015
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. Additionally, MGE has defined contribution 401(k) benefit plans.
	The following table presents the components of MGE Energy's and MGE's net periodic benefit costs recognized for the three months ended March 31, 2015 and 2014. A portion of the net periodic benefit cost is capitalized within the consolidated balance sheets.
				Three Months Ended
				March 31,
		(In thousands)		2015		2014
		Pension Benefits
		Components of net periodic cost (benefit):
		Service cost	$	1,798	$	1,484
		Interest cost		3,440		3,251
		Expected return on assets		-5,677		-5,279
		Amortization of:
		Prior service cost		6		49
		Actuarial loss		1,334		173
		Net periodic cost (benefit)	$	901	$	-322
		Postretirement Benefits
		Components of net periodic cost (benefit):
		Service cost	$	383	$	330
		Interest cost		778		772
		Expected return on assets		-703		-654
		Amortization of:
		Transition obligation		1		1
		Prior service benefit		-667		-668
		Actuarial loss		262		39
		Net periodic cost (benefit)	$	54	$	-180

ShareBased_Compensation

Share-Based Compensation	3 Months Ended
	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	Share-Based Compensation - MGE Energy and MGE.
	Under MGE Energy's Performance Unit Plan, eligible employees may receive performance units that entitle the holder to receive a cash payment equal to the value of a designated number of shares of MGE Energy's common stock, plus dividend equivalent payments thereon, at the end of the set performance period.
	On February 20, 2015, 18,948 units were granted based on the MGE Energy closing stock price as of that date. Units are subject to a five-year graded vesting schedule. On the grant date, MGE Energy and MGE measure the cost of the employee services received in exchange for a performance unit award based on the current market value of MGE Energy common stock. The fair value of the awards has been subsequently re-measured at March 31, 2015, as required by applicable accounting standards. Changes in fair value have been recognized as compensation cost. Since this amount is re-measured quarterly throughout the vesting period, the compensation cost is subject to variability.
	For nonretirement eligible employees, stock based compensation costs are accrued and recognized using the graded vesting method. Compensation cost for retirement eligible employees or employees that will become retirement eligible during the vesting schedule are recognized on an abridged horizon.
	In December 2013, a Director Incentive Plan was approved for the non-employee members of the Board of Directors. This plan is similar to MGE Energy's Performance Unit Plan for eligible employees described above. Under the plan, a non-employee director can receive performance units that entitle the holder to receive a cash payment equal to the value of a designated number of shares of MGE Energy's common stock, plus dividend payments, at the end of the set performance period. The units are subject to a three-year graded vesting schedule. In January 2015, 3,794 units were granted. For accounting purposes, the awards will be measured similarly to the employee unit awards.
	During the three months ended March 31, 2015 and 2014, MGE recorded $0.5 million and $0.8 million, respectively, in compensation expense as a result of awards under the plans. In January 2015, cash payments of $1.3 million were distributed relating to awards that were granted in 2010. During the three months ended March 31, 2015, MGE recorded $0.2 million of forfeitures as the result of the forfeiture of 4,676 units. No forfeitures occurred during the three months ended March 31, 2014. At March 31, 2015, $5.3 million of outstanding awards are vested, and of this amount no cash settlements have occurred.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies - MGE Energy and MGE.
	a. Environmental.
	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 they conduct their operations, the costs of those operations, as well as capital and operating expenditures. Regulatory initiatives, proposed rules, and court challenges to adopted rules, have the potential to have a material effect on our capital expenditures and operating costs. These initiatives, proposed rules, and court challenges include:
	EPA's Proposed Effluent Limitations Guidelines (ELG) and Standards for Steam Electric Power Generating Point Source Category
	The EPA published a proposed rule in June 2013 that would amend the current ELG rule and lower the existing permissible water discharge of metals and other pollutants in wastewater from new and existing steam electric generation plants. The proposed rule mostly covers certain air pollution control systems and ash handling systems at coal-burning power plants with units greater than 50 megawatt (MW) generation capacity. The EPA is under a consent decree to finalize the rule by September 2015. Once finalized, the rule will apply to power plants as they renew their WPDES permits beginning in July 2017.
	Based on our current evaluation of the proposed rule and its alternatives, our Elm Road Units and Columbia plant may need to add treatment systems or additional equipment, and those additions may be significant. However, MGE cannot estimate those costs with any certainty until we are able to evaluate the final version of this rule. Management believes compliance costs will be recovered in rates based on previous treatment of environmental compliance projects.
	EPA Cooling Water Intake Rules (Section 316(b))
	Section 316(b) of the CWA requires that the cooling water intake structures at electric power plants meet best available technology standards so that mortality from entrainment (drawing aquatic life into a plant's cooling system) and impingement (trapping aquatic life on screens) are reduced. The EPA finalized its 316(b) rule for existing facilities in 2014. Section 316(b) requirements are implemented in Wisconsin through modifications to plants' WPDES permits, which govern plant water discharges. WDNR is currently developing rules to implement the EPA 316(b) rule.
	Our WCCF facility already employs a system that meets the 316(b) rule. Our Blount plant has conducted studies showing that it will likely be in compliance with this rule. The operator of our Columbia plant plans to conduct an intake study to demonstrate compliance with this rule and/or identify design criteria needed to meet the new rule requirements prior to Columbia's 2017 permit renewal. The exact requirements at Blount and Columbia, however, will not be known until the WNDR finalizes its rule, approves the operators' approach, and those sites' permits are modified to account for this rule. Nonetheless, MGE expects that the 316(b) rule will not have material effects on its existing plants.
	EPA's Greenhouse Gas (GHG) Reduction Guidelines under the Clean Air Act 111d Rule
	In June 2014, the EPA developed a proposed rule called the Clean Power Plan that set guidelines for states to use in developing plans to control GHG emissions from existing fossil fuel fired electric generating units (EGUs). The EPA's proposal includes reductions in GHG emissions from EGUs by a national average of 30% by 2030 as measured from a 2012 baseline. Each state is given its own emission reduction targets to meet this goal, and States' goals can be higher or lower than the national average. The State of Wisconsin's reduction goal is 34%. These targets are expressed as a "rate-based" emission average to be achieved by the combined fleet of EGUs within the state. States would be expected to develop, submit and implement a plan for the reduction goals, and make "meaningful progress" towards these reductions by 2020 and to meet their respective targets by 2030.
	The EPA's rule is expected to be finalized mid-summer 2015. States will then have up to two years to prepare their compliance plans. While there is currently no certainty regarding the terms of the final rule, it is reasonable to assume that this rule will have a material impact on MGE. The parameters of the final rule, however, will determine the extent to which this rule will affect MGE.
	National Ambient Air Quality Standards (NAAQS)
	The EPA's NAAQS regulations have been developed to set ambient levels of six pollutants to protect sensitive populations (primary NAAQS) and the environment (secondary NAAQS) from the negative effects of exposure to these pollutants at higher levels. MGE is following developments for several NAAQS, including for particulate matter, nitrogen dioxide, sulfur dioxide, and ozone. Further discussion on sulfur dioxide and ozone NAAQS follows. For additional information on the NAAQS process, see Footnote 18.d. of Notes to Consolidated Financial Statements under Item 8, Financial Statements and Supplementary Data, of MGE Energy's and MGE's 2014 Annual Report on Form 10-K.
	Sulfur Dioxide (SO2) NAAQS
	The EPA's new 1-hour SO2 NAAQS has been in place since 2010 and initial attainment/nonattainment designations by states were due in 2013. However, the EPA was sued by environmental groups for not timely and properly making these designations. In March 2015, the EPA entered into a court-approved consent decree requiring 1-hour SO2 attainment/nonattainment area designations to be completed in three phases extending out until 2020. States must submit their first designation proposals in September 2015 encompassing those areas that contain large stationary sources of SO2 (sources that emit over a threshold mass of SO2, and/or over a threshold emissions rate). The EPA must make final designation determinations for these areas by July 2016.
	In March 2015, MGE's Columbia plant was identified in the Federal Register as meeting the criteria of a large stationary source of SO2 (based on 2012 data). As such, the State of Wisconsin must submit an attainment/nonattainment area designation for Columbia County (the county in which the Columbia plant resides). Since the 2012 data was collected, Columbia has installed pollution control equipment that has lowered its total SO2 emissions and its SO2 emissions rate. However, we will not know with any certainty if Columbia County will be determined to be in attainment until the State of Wisconsin completes its attainment/nonattainment demonstration. The outcome of this designation may have an adverse effect on the operation of the Columbia plant. MGE will monitor and participate in developments with the Columbia County designation process.
	Ozone NAAQS
	MGE is monitoring developments in the EPA's revision of the Ozone NAAQS rule. In November 2014, the EPA published proposed regulations to lower the Ozone NAAQS to between 65 to 70 parts per billion (ppb). In this proposed rule, the EPA has stated they are also considering leaving the standard at its current level of 75 ppb, or lowering it further to 60 ppb. The EPA is seeking comments on these options. In addition, the EPA is proposing a secondary ozone standard that would use a new index to measure ecosystem and vegetation effects. It is not clear how this secondary standard would affect sources. Milwaukee County (where our Elm Road Units are located) and Dane and Columbia Counties (where several of our facilities are located) may not meet the Ozone NAAQS if it is lowered to 70 ppb or below. The EPA plans to have a final Ozone NAAQS rule completed by the end of 2015. MGE will continue to monitor rule developments and subsequent state actions and implementation plans.
	EPA's Cross-State Air Pollution Rule
	In July 2011, the EPA finalized its Cross-State Air Pollution Rule (CSAPR) as a court-ordered replacement for its Clean Air Interstate Rule (CAIR) that had been remanded in 2008. CSAPR is an interstate air pollution transport rule designed to reduce ozone and fine particulate matter (PM2.5) air levels in areas that the EPA has determined are being affected by pollution from neighboring and upwind states.
	CSAPR has been the subject of extensive litigation. Although many aspects of CSAPR have been upheld on appeal, the litigation has delayed implementation and created uncertainty. In late 2014, the EPA tolled CSAPR's original compliance deadlines by three years and MGE's affected facilities must now meet their Phase I reduction obligations in 2015 and Phase II in 2017. However, the ongoing litigation leaves unresolved several residual issues that may affect whether, when, and how MGE's facilities will need to comply with CSAPR. Regardless, MGE expects to be able to meet CSAPR requirements at all of our applicable facilities by applying reductions achieved from recent pollution control installations and early reduction efforts. We will continue to monitor developments.
	Clean Air Visibility Rule (CAVR)
	Columbia may be subject to the best available retrofit technology (BART) regulations, a subsection of the EPA's Clean Air Visibility Rule (CAVR), which may require pollution control retrofits. Columbia's pollution control upgrades and the EPA's stance that compliance with the CSAPR equals compliance with BART should mean that Columbia will not need to do additional work to meet BART requirements. At this time, however, the BART regulatory obligations, compliance strategies, and costs remain uncertain due to the legal uncertainty surrounding CSAPR.
	EPA's Coal Combustion Residuals Rule
	In December 2014, the EPA finalized its Disposal of Coal Combustion Residuals from Electric Utilities rule. The rule will go into effect six months after it is published in the Federal Register. The EPA has delayed publication of this rule and has indicated that it plans to publish the rule during the second quarter of 2015. The rule provides that coal ash will be regulated as a solid waste and defines what ash use activities would be considered beneficial use of coal ash. The rule also regulates landfills, ash ponds, and other surface impoundments for coal combustion residuals (CCRS or coal ash) by regulating their design, location, monitoring, and operation. Landfills and impoundments that cannot meet design criteria will need to formally close within defined timeframes.
	The Columbia and Elm Road Units co-owners and plant operators are evaluating the final rule to determine what changes may be necessary at those facilities and the associated timeframes. We anticipate that some design and operational changes may need to be made at these facilities. Preliminary review for our Elm Road facility has indicated that the costs may not be significant. We are still evaluating the rule’s full effects at Columbia. Management believes compliance costs will be recovered in rates based on previous treatment of environmental compliance projects.
	Columbia
	Based upon current available information, compliance with various environmental requirements and initiatives is expected to result in significant additional operating and capital expenditures at Columbia as noted below.
	Columbia Clean Air Act Litigation
	Columbia is a coal-fired generating station operated by WPL in which WPL, WPSC, and MGE have ownership interests. In December 2009, the EPA sent a Notice of Violation (NOV) to MGE as one of the co-owners of Columbia. The NOV alleged that WPL and the Columbia co-owners failed to comply with appropriate pre-construction review and permitting requirements and, as a result, violated the Prevention of Significant Deterioration program requirements, Title V Operating Permit requirements of the CAA, and the Wisconsin SIP. In April 2013, the EPA filed a lawsuit against the co-owners of Columbia asserting similar allegations. In September 2010 and April 2013, the Sierra Club filed civil lawsuits against WPL alleging violations of the CAA at Columbia and other Wisconsin facilities operated by WPL. In June 2013, the court approved and entered a consent decree entered by the EPA, Sierra Club, and the co-owners of Columbia to resolve these claims, while admitting no liability. One of the requirements of the consent decree requires installation of a SCR system at Columbia Unit 2 by December 31, 2018. Installation of the SCR has been approved by the PSCW. MGE's share of the projected cost for the SCR system is approximately $30-$40 million. In addition, the consent decree establishes emission rate limits for SO2, NOx, and particulate matter and annual plant-wide emission caps for SO2 and NOx. MGE intends to seek recovery in rates of the costs associated with its compliance with the terms of the final consent decree and currently expects to recover any material compliance costs.
	b. Legal Matters.
	MGE is involved in various legal matters that are being defended and handled in the normal course of business. MGE maintains accruals for such 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.

Derivative_and_Hedging_Instrum

Derivative and Hedging Instruments	3 Months Ended
	Mar. 31, 2015
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, MGE Energy and MGE recognize such derivatives in the consolidated balance sheets at fair value. MGE's 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 years. If the derivative qualifies for regulatory deferral, the derivatives are marked to fair value and are offset with a corresponding regulatory asset or liability. The deferred gain or loss is recognized in earnings in the delivery month applicable to the instrument. Gains and losses related to hedges qualifying for regulatory treatment are recoverable in gas rates through the PGA or in electric rates as a component of the fuel rules mechanism.
	b. Notional Amounts.
	The gross notional volume of open derivatives is as follows:
			31-Mar-15		31-Dec-14
		Commodity derivative contracts	408,920 MWh		448,000 MWh
		Commodity derivative contracts	2,785,000 Dth		4,405,000 Dth
		FTRs	691 MW		1,854 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 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. At March 31, 2015 and December 31, 2014, the cost basis of exchange traded derivatives and FTRs exceeded their fair value by $0.6 million and $1.6 million, respectively.
	MGE is a party to a ten-year 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 sheet. 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 at March 31, 2015 and December 31, 2014, reflects a loss position of $53.4 million. The actual fuel cost will be recognized in purchased power expense in the month of purchase and collected in rates.
	The following table summarizes the fair value of the derivative instruments on the consolidated balance sheet. 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, MGE Energy and MGE have netted instruments with the same counterparty under a master netting agreement as well as the netting of collateral. At March 31, 2015, MGE Energy and MGE had the right to reclaim collateral (a receivable) of $0.6 million.
			Asset Derivatives				Liability Derivatives
	(In thousands)		Balance Sheet Location		Fair Value		Balance Sheet Location		Fair Value
	31-Mar-15
	Commodity derivative contracts		Other current assets	$	336		Derivative liability (current)	$	821
	Commodity derivative contracts		Other deferred charges		7		Derivative liability (long-term)		116
	FTRs		Other current assets		38		Derivative liability (current)		-
	Ten-year PPA		N/A		N/A		Derivative liability (current)		7,090
	Ten-year PPA		N/A		N/A		Derivative liability (long-term)		46,320
	31-Dec-14
	Commodity derivative contracts		Other current assets	$	130		Derivative liability (current)	$	2,262
	Commodity derivative contracts		Other deferred charges		93		Derivative liability (long-term)		171
	FTRs		Other current assets		642		Derivative liability (current)		-
	Ten-year PPA		N/A		N/A		Derivative liability (current)		6,870
	Ten-year PPA		N/A		N/A		Derivative liability (long-term)		46,560
	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 sheet.
		Offsetting of Derivative Assets
		(In thousands)		Gross amounts		Gross amounts offset in balance sheet		Collateral posted against derivative positions		Net amount presented in balance sheet
		31-Mar-15
		Commodity derivative contracts	$	343	$	-343	$	-	$	-
		FTRs		38		-		-		38
		31-Dec-14
		Commodity derivative contracts	$	223	$	-223	$	-	$	-
		FTRs		642		-		-		642
		Offsetting of Derivative Liabilities
		(In thousands)		Gross amounts		Gross amounts offset in balance sheet		Collateral posted against derivative positions		Net amount presented in balance sheet
		31-Mar-15
		Commodity derivative contracts	$	937	$	-343	$	-565	$	29
		Ten-year PPA		53,410		-		-		53,410
		31-Dec-14
		Commodity derivative contracts	$	2,433	$	-223	$	-2,179	$	31
		Ten-year PPA		53,430		-		-		53,430
	The following tables summarize the unrealized and realized gains (losses) related to the derivative instruments on the consolidated balance sheet at March 31, 2015 and 2014, and the consolidated income statement for the three months ended March 31, 2015 and 2014.
			2015					2014
	(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,	$	54,998	$	1,001		$	63,893	$	411
	Change in unrealized (loss) gain		1,318		-			-13,601		-
	Realized (loss) gain reclassified to a deferred account		-1,061		1,061			1,535		-1,535
	Realized gain (loss) reclassified to income
	statement		-1,289		-1,794			6,386		1,475
	Balance at March 31,	$	53,966	$	268		$	58,213	$	351
			Realized losses (gains)
			2015					2014
	(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	$	420	$	1,761		$	-4,795	$	-1,220
	FTRs		-119		-			-636		-
	Ten-year PPA		1,021		-			-1,210		-
	MGE's commodity derivative contracts, FTRs, and ten-year 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 sheet and are recognized in earnings in the delivery month applicable to the instrument. As a result of the above described treatment, there are no unrealized gains or losses that flow through earnings.
	The ten-year 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, 2015, no collateral has 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, 2015 and December 31, 2014, certain counterparties were in a net liability of less than $0.1 million.
	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, 2015, no counterparties have defaulted.

Rate_Matters

Rate Matters	3 Months Ended
	Mar. 31, 2015
Regulated Operations [Abstract]
Rate Matters	Rate Matters - MGE Energy and MGE.
	a. Rate Proceedings.
	On December 23, 2014, the PSCW authorized MGE to increase 2015 rates for retail electric customers by 3.8% or $15.4 million and to decrease gas rates by 2.0% or $3.8 million. The increase in retail electric rates cover costs associated with the construction of emission-reduction equipment at Columbia, improvements and reliability of the state's electric transmission system, fuel and purchased power related to coal delivery costs, partially offset by lower cost as a result of market conditions for pension and post-retirement benefit costs. The authorized return on common stock equity is 10.2%.
	The PSCW approved changes to customer rates and rate design for gas service. Gas rate design consists of a fixed monthly customer charge and a variable charge tied to actual usage, in addition to the separate charge for natural gas commodity costs (PGA). The change shifted more of the rate recovery to the monthly charge, reflecting the related fixed costs of providing gas services, and reduced the variable usage-based charge. Thus, gas net income is expected to be more evenly distributed during the year and less sensitive to weather. A similar, but much smaller rate design shift was also approved for electric rates.
	On July 26, 2013, the PSCW authorized MGE to freeze electric and natural gas rates at 2013 levels for 2014. The order authorized 100% AFUDC on the Columbia scrubber construction project and deferral of increased costs related to ATC and MISO network upgrade fees. As part of the rate freeze plan authorized by the PSCW, effective January 1, 2014, approximately $6.3 million associated with a 2012 fuel rule surplus credit was required to be refunded to customers and was amortized in 2014. The fuel credit accrued interest at MGE's weighted cost of capital. The authorized return on equity remained unchanged at 10.3%.
	b. Fuel Rules.
	Fuel rules require the PSCW and 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 most recent base rate proceedings. Any over/under recovery of the actual costs is determined on an annual basis and will be adjusted in future billings to electric retail customers. The fuel rules bandwidth is currently set at plus or minus 2%. Under fuel rules, MGE would defer costs, less any excess revenues, if its actual electric fuel costs exceeded 102% 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 98% of the electric fuel costs allowed in that order.
	As of March 31, 2015, MGE has deferred $2.4 million (to be returned to customers in a future period) of 2015 electric fuel-related savings that are outside the range authorized by the PSCW. As part of the rate freeze plan authorized by the PSCW for 2014, $1.6 million of the approximately $6.3 million associated with the 2012 fuel rule credit was amortized against purchased power expense during the three months ended March 31, 2014.
	c. Purchased Gas Adjustment Clause.
	MGE's natural gas rates are subject to a fuel adjustment clause designed to recover or refund the difference between the actual cost of purchased gas and the amount included in rates. Differences between the amounts billed to customers and the actual costs recoverable are deferred and recovered or refunded in future periods by means of prospective monthly adjustments to rates. At March 31, 2015 and December 31, 2014, MGE had over collected $6.7 million and $1.2 million, respectively, which was recorded in other current liabilities on the consolidated balance sheets.

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2015
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.
	At March 31, 2015 and December 31, 2014, 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 MGE Energy's and MGE's long-term debt is based on quoted market prices for similar financial instruments at March 31, 2015 and December 31, 2014. Since long-term debt is not traded in an active market, it is classified as Level 2. The estimated fair market value of MGE Energy's and MGE's financial instruments are as follows:
				31-Mar-15					31-Dec-14
		(In thousands)		Carrying Amount		Fair Value			Carrying Amount		Fair Value
		MGE Energy
		Assets:
		Cash and cash equivalents	$	70,703	$	70,703		$	65,755	$	65,755
		Liabilities:
		Short-term debt - commercial paper		-		-			7,000		7,000
		Long-term debt*		398,653		465,534			399,690		457,420
		MGE
		Assets:
		Cash and cash equivalents	$	17,156	$	17,156		$	4,562	$	4,562
		Liabilities:
		Short-term debt - commercial paper		-		-			7,000		7,000
		Long-term debt*		398,653		465,534			399,690		457,420
		*Includes long-term debt due within one year.
	b. Recurring Fair Value Measurements.
	The following table presents the balances of assets and liabilities measured at fair value on a recurring basis for MGE Energy and MGE.
				Fair Value as of March 31, 2015
		(In thousands)		Total		Level 1		Level 2		Level 3
		MGE Energy
		Assets:
		Derivatives, net	$	38	$	-	$	-	$	38
		Exchange-traded investments		786		786		-		-
		Total Assets	$	824	$	786	$	-	$	38
		Liabilities:
		Derivatives, net(a)	$	54,004	$	100	$	-	$	53,904
		Deferred compensation		2,958		-		2,958		-
		Total Liabilities	$	56,962	$	100	$	2,958	$	53,904
		MGE
		Assets:
		Derivatives, net	$	38	$	-	$	-	$	38
		Exchange-traded investments		214		214		-		-
		Total Assets	$	252	$	214	$	-	$	38
		Liabilities:
		Derivatives, net(a)	$	54,004	$	100	$	-	$	53,904
		Deferred compensation		2,958		-		2,958		-
		Total Liabilities	$	56,962	$	100	$	2,958	$	53,904
				Fair Value as of December 31, 2014
		(In thousands)		Total		Level 1		Level 2		Level 3
		MGE Energy
		Assets:
		Derivatives, net	$	642	$	-	$	-	$	642
		Exchange-traded investments		927		927		-		-
		Total Assets	$	1,569	$	927	$	-	$	642
		Liabilities:
		Derivatives, net(a)	$	55,640	$	1,012	$	-	$	54,628
		Deferred compensation		2,832		-		2,832		-
		Total Liabilities	$	58,472	$	1,012	$	2,832	$	54,628
		MGE
		Assets:
		Derivatives, net	$	642	$	-	$	-	$	642
		Exchange-traded investments		350		350		-		-
		Total Assets	$	992	$	350	$	-	$	642
		Liabilities:
		Derivatives, net(a)	$	55,640	$	1,012	$	-	$	54,628
		Deferred compensation		2,832		-		2,832		-
		Total Liabilities	$	58,472	$	1,012	$	2,832	$	54,628
	(a) These amounts are shown gross and exclude $0.6 million and $2.2 million of collateral that was
	posted against derivative positions with counterparties as of March 31, 2015 and
	December 31, 2014, respectively.
No transfers were made in or out of Level 1 or Level 2 for the three months ended March 31, 2015.
Investments include exchange-traded investment securities valued using quoted prices on active exchanges and are therefore classified as Level 1.
Derivatives include exchange-traded derivative contracts, over-the-counter transactions, a ten-year 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 classified as Level 3. Transactions done with an over-the-counter party are on inactive markets and are therefore considered unobservable and 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 ten-year purchased power agreement (see Footnote 9) was valued using an internally-developed 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, where such exchange-traded contracts exist, and upon calculations based on forward gas prices, where such exchange-traded contracts do not exist. 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.
This model is prepared by members of MGE's Energy Accounting group. It is reviewed on a quarterly basis by management in Energy Supply and Finance to review the assumptions, inputs, and fair value measurements.
The following table presents the significant unobservable inputs used in the pricing model.
			Model Input
	Significant Unobservable Inputs		31-Mar-15		31-Dec-14
	Basis adjustment:
	On peak		97.50%		98.10%
	Off peak		94.70%		95.00%
	Counterparty fuel mix:
	Internal generation		60% - 75%		50% - 70%
	Purchased power		40% - 25%		50% - 30%
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 of MGE Energy and MGE. The notional investments earn interest based upon the semiannual rate of U.S. Treasury Bills having a 26 week maturity increased by 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.
The following table summarizes the changes in Level 3 assets and liabilities measured at fair value on a recurring basis for both MGE Energy and MGE.
			Three Months Ended
			March 31,
	(In thousands)		2015		2014
	Beginning balance	$	-53,986	$	-64,628
	Realized and unrealized gains (losses):
	Included in regulatory liabilities		119		5,831
	Included in other comprehensive income		-		-
	Included in earnings		-1,328		6,634
	Included in current assets		-		-53
	Purchases		6,162		6,859
	Sales		34		-60
	Issuances		-		-
	Settlements		-4,867		-13,380
	Transfers in and/or out of Level 3		-		-
	Balance as of March 31,	$	-53,866	$	-58,797
	Total gains (losses) included in earnings attributed to the change in unrealized gains (losses) related to assets and liabilities held at March 31,(b)	$	-	$	-
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 for both MGE Energy and MGE (b).
			Three Months Ended
			March 31,
	(In thousands)		2015		2014
	Purchased Power Expense	$	-1,328	$	6,634
(b) MGE's exchange-traded derivative contracts, over-the-counter party transactions, ten-year 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.

New_Accounting_Pronouncements

New Accounting Pronouncements	3 Months Ended
	Mar. 31, 2015
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New Accounting Pronouncements	New Accounting Pronouncements - MGE Energy and MGE.
	a. Transfers and Servicing Assets.
	In June 2014, the FASB issued authoritative guidance within the Codification's Transfers and Servicing topic that provides guidance on the accounting and disclosures for repurchase-to-maturity transactions, securities lending transactions, and repurchase financings. This authoritative guidance became effective January 1, 2015. The authoritative guidance changed the accounting for the Chattel Paper program and required additional disclosures. Prior to adoption of the standard, Chattel Paper was treated as an off-balance sheet arrangement. See Footnote 4 for additional information.
	b. Revenue from Contracts with Customers.
	In May 2014, the FASB issued authoritative guidance within the Codification's Revenue Recognition topic that provides guidance on the recognition, measurement, and disclosure of revenue from contracts with customers. This authoritative guidance is currently scheduled to become effective January 1, 2017. In April 2015, the FASB proposed to defer the effective date to January 1, 2018. MGE Energy and MGE are currently assessing the impact this pronouncement will have on their financial statements.
	c. Consolidations.
	In February 2015, the FASB issued authoritative guidance within the Codification’s Consolidation topic that provides guidance on the evaluation of certain legal entities for consolidation purposes. This authoritative guidance will become effective January 1, 2016. MGE Energy and MGE are currently assessing the impact this pronouncement will have on their financial statements.
	d. Debt Issuance Costs.
	In April 2015, the FASB issued authoritative guidance within the Codification’s Interest topic that provides guidance on the presentation of debt issuance costs in financial statements. This authoritative guidance will become effective January 1, 2016. The authoritative guidance changes the presentation of debt issuance costs on the balance sheet from an asset to a direct deduction from the related debt liability. The impact of this guidance on our financial statements is not expected to be material.
	e. Cloud Computing Arrangements.
	In April 2015, the FASB issued authoritative guidance within the Codification’s Software topic that provides guidance on the accounting treatment of cloud computer arrangements. This authoritative guidance will become effective January 1, 2016. The authoritative guidance provides criteria for determining whether a cloud computing arrangement contains a software license that should be accounted for as internal-use software. The impact of this guidance on our financial statements is not expected to be material.

Segment_Information

Segment Information	3 Months Ended
	Mar. 31, 2015
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 MGE Energy's and MGE's 2014 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		Non- Regulated Energy		Transmission Investment		All Others		Consolidation/ Elimination Entries		Consolidated Total
	Three Months Ended March 31, 2015
	Operating revenues	$	98,240	$	69,928	$	1,966	$	-	$	-	$	-	$	170,134
	Interdepartmental revenues		115		2,725		9,847		-		-		-12,687		-
	Total operating revenues		98,355		72,653		11,813		-		-		-12,687		170,134
	Depreciation and amortization		-7,332		-1,642		-1,863		-		-12		-		-10,849
	Other operating expenses		-79,800		-60,068		-50		-		-203		12,687		-127,434
	Operating income (loss)		11,223		10,943		9,900		-		-215		-		31,851
	Other (deductions) income, net		90		-1		-		1,881		135		-		2,105
	Interest (expense) income, net		-2,819		-804		-1,518		-		50		-		-5,091
	Income (loss) before taxes		8,494		10,138		8,382		1,881		-30		-		28,865
	Income tax provision		-2,383		-4,081		-3,364		-756		-3		-		-10,587
	Net income (loss)	$	6,111	$	6,057	$	5,018	$	1,125	$	-33	$	-	$	18,278
	Three Months Ended March 31, 2014
	Operating revenues	$	98,852	$	110,713	$	680	$	-	$	-	$	-	$	210,245
	Interdepartmental revenues		118		3,624		10,670		-		-		-14,412		-
	Total operating revenues		98,970		114,337		11,350		-		-		-14,412		210,245
	Depreciation and amortization		-6,337		-1,563		-1,834		-		-12		-		-9,746
	Other operating expenses		-77,901		-92,843		-40		-		-156		14,412		-156,528
	Operating income (loss)		14,732		19,931		9,476		-		-168		-		43,971
	Other (deductions) income, net		1,827		-35		-		2,481		279		-		4,552
	Interest (expense) income, net		-2,205		-804		-1,572		-		40		-		-4,541
	Income before taxes		14,354		19,092		7,904		2,481		151		-		43,982
	Income tax provision		-4,353		-7,665		-3,172		-998		-77		-		-16,265
	Net income	$	10,001	$	11,427	$	4,732	$	1,483	$	74	$	-	$	27,717
	The following tables show segment information for MGE's operations for the indicated periods:
	(In thousands)MGE		Electric		Gas		Non- Regulated Energy		Transmission Investment		Consolidation/ Elimination Entries		Consolidated Total
	Three Months Ended March 31, 2015
	Operating revenues	$	98,245	$	69,933	$	1,966	$	-	$	-	$	170,144
	Interdepartmental revenues		110		2,720		9,847		-		-12,677		-
	Total operating revenues		98,355		72,653		11,813		-		-12,677		170,144
	Depreciation and amortization		-7,332		-1,642		-1,863		-		-		-10,837
	Other operating expenses*		-82,142		-64,138		-3,414		-		12,677		-137,017
	Operating income*		8,881		6,873		6,536		-		-		22,290
	Other (deductions) income, net*		49		-12		-		1,125		-		1,162
	Interest expense, net		-2,819		-804		-1,518		-		-		-5,141
	Net income		6,111		6,057		5,018		1,125		-		18,311
	Less: Net income attributable to
	noncontrolling interest, net of tax		-		-		-		-		-6,553		-6,553
	Net income attributable to MGE	$	6,111	$	6,057	$	5,018	$	1,125	$	-6,553	$	11,758
	Three Months Ended March 31, 2014
	Operating revenues	$	98,858	$	110,718	$	680	$	-	$	-	$	210,256
	Interdepartmental revenues		112		3,619		10,670		-		-14,401		-
	Total operating revenues		98,970		114,337		11,350		-		-14,401		210,256
	Depreciation and amortization		-6,337		-1,563		-1,834		-		-		-9,734
	Other operating expenses*		-82,046		-100,450		-3,212		-		14,401		-171,307
	Operating income*		10,587		12,324		6,304		-		-		29,215
	Other (deductions) income, net*		1,619		-93		-		1,483		-		3,009
	Interest expense, net		-2,205		-804		-1,572		-		-		-4,581
	Net income		10,001		11,427		4,732		1,483		-		27,643
	Less: Net income attributable to
	noncontrolling interest, net of tax		-		-		-		-		-6,510		-6,510
	Net income attributable to MGE	$	10,001	$	11,427	$	4,732	$	1,483	$	-6,510	$	21,133
	*Amounts are shown net of the related tax expense, consistent with the presentation on the consolidated MGE Income Statement.

Significant_Accounting_Policie

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2015
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 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.
Common Stock	MGE Energy sells shares of its common stock through its Stock Plan. Those shares may be newly issued shares or shares that MGE Energy has purchased in the open market for resale to 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.
Investments - ATC	MGE Transco has accounted for its investment in ATC under the equity method of accounting.
Chattel Paper Agreement	MGE makes available to qualifying customers a financing program for the purchase and installation of energy-related equipment that will provide more efficient use of utility service at the customer's property. The energy-related equipment installed at the customer sites is used to secure the customer loans. MGE is party to a chattel paper purchase agreement with a financial institution under which it can sell or finance an undivided interest with recourse, in up to $10.0 million of the financing program receivables, until July 31, 2015. The length of the MGE guarantee to the financial institution varies from one to ten years depending on the term of the underlying customer loan. The loan balances outstanding at March 31, 2015, approximate the fair value of the energy-related equipment acting as collateral. MGE accounts for these agreements as secured borrowings.
	Prior to authoritative guidance that became effective in 2015, these agreements were treated as off-balance sheet arrangements. Beginning January 1, 2015, these agreements are included as assets and liabilities in the consolidated balance sheet. As of March 31, 2015, assets (other accounts receivable and other deferred assets) and liabilities (accounts payable and other deferred liabilities) increased approximately $4.3 million as a cumulative result of the guidance. In addition, the cumulative effect of this guidance resulted in a $0.1 million reduction in retained earnings.
Share-based Compensation	Under MGE Energy's Performance Unit Plan, eligible employees may receive performance units that entitle the holder to receive a cash payment equal to the value of a designated number of shares of MGE Energy's common stock, plus dividend equivalent payments thereon, at the end of the set performance period.
	On February 20, 2015, 18,948 units were granted based on the MGE Energy closing stock price as of that date. Units are subject to a five-year graded vesting schedule. On the grant date, MGE Energy and MGE measure the cost of the employee services received in exchange for a performance unit award based on the current market value of MGE Energy common stock. The fair value of the awards has been subsequently re-measured at March 31, 2015, as required by applicable accounting standards. Changes in fair value have been recognized as compensation cost. Since this amount is re-measured quarterly throughout the vesting period, the compensation cost is subject to variability.
	For nonretirement eligible employees, stock based compensation costs are accrued and recognized using the graded vesting method. Compensation cost for retirement eligible employees or employees that will become retirement eligible during the vesting schedule are recognized on an abridged horizon.
	In December 2013, a Director Incentive Plan was approved for the non-employee members of the Board of Directors. This plan is similar to MGE Energy's Performance Unit Plan for eligible employees described above. Under the plan, a non-employee director can receive performance units that entitle the holder to receive a cash payment equal to the value of a designated number of shares of MGE Energy's common stock, plus dividend payments, at the end of the set performance period. The units are subject to a three-year graded vesting schedule. In January 2015, 3,794 units were granted. For accounting purposes, the awards will be measured similarly to the employee unit awards.
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, MGE Energy and MGE recognize such derivatives in the consolidated balance sheets at fair value. MGE's 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 years. If the derivative qualifies for regulatory deferral, the derivatives are marked to fair value and are offset with a corresponding regulatory asset or liability. The deferred gain or loss is recognized in earnings in the delivery month applicable to the instrument. Gains and losses related to hedges qualifying for regulatory treatment are recoverable in gas rates through the PGA or in electric rates as a component of the fuel rules mechanism.
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, MGE Energy and MGE have netted instruments with the same counterparty under a master netting agreement as well as the netting of collateral.
Wisconsin Fuel Rules	Fuel rules require the PSCW and 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 most recent base rate proceedings. Any over/under recovery of the actual costs is determined on an annual basis and will be adjusted in future billings to electric retail customers. The fuel rules bandwidth is currently set at plus or minus 2%. Under fuel rules, MGE would defer costs, less any excess revenues, if its actual electric fuel costs exceeded 102% 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 98% of the electric fuel costs allowed in that order.
Purchased Gas Adjustment Clause	MGE's natural gas rates are subject to a fuel adjustment clause designed to recover or refund the difference between the actual cost of purchased gas and the amount included in rates. Differences between the amounts billed to customers and the actual costs recoverable are deferred and recovered or refunded in future periods by means of prospective monthly adjustments to rates. At March 31, 2015 and December 31, 2014, MGE had over collected $6.7 million and $1.2 million, respectively, which was recorded in other current liabilities on the consolidated balance sheets.
New Accounting Pronouncements Disclosure	New Accounting Pronouncements - MGE Energy and MGE.
	a. Transfers and Servicing Assets.
	In June 2014, the FASB issued authoritative guidance within the Codification's Transfers and Servicing topic that provides guidance on the accounting and disclosures for repurchase-to-maturity transactions, securities lending transactions, and repurchase financings. This authoritative guidance became effective January 1, 2015. The authoritative guidance changed the accounting for the Chattel Paper program and required additional disclosures. Prior to adoption of the standard, Chattel Paper was treated as an off-balance sheet arrangement. See Footnote 4 for additional information.
	b. Revenue from Contracts with Customers.
	In May 2014, the FASB issued authoritative guidance within the Codification's Revenue Recognition topic that provides guidance on the recognition, measurement, and disclosure of revenue from contracts with customers. This authoritative guidance is currently scheduled to become effective January 1, 2017. In April 2015, the FASB proposed to defer the effective date to January 1, 2018. MGE Energy and MGE are currently assessing the impact this pronouncement will have on their financial statements.
	c. Consolidations.
	In February 2015, the FASB issued authoritative guidance within the Codification’s Consolidation topic that provides guidance on the evaluation of certain legal entities for consolidation purposes. This authoritative guidance will become effective January 1, 2016. MGE Energy and MGE are currently assessing the impact this pronouncement will have on their financial statements.
	d. Debt Issuance Costs.
	In April 2015, the FASB issued authoritative guidance within the Codification’s Interest topic that provides guidance on the presentation of debt issuance costs in financial statements. This authoritative guidance will become effective January 1, 2016. The authoritative guidance changes the presentation of debt issuance costs on the balance sheet from an asset to a direct deduction from the related debt liability. The impact of this guidance on our financial statements is not expected to be material.
	e. Cloud Computing Arrangements.
	In April 2015, the FASB issued authoritative guidance within the Codification’s Software topic that provides guidance on the accounting treatment of cloud computer arrangements. This authoritative guidance will become effective January 1, 2016. The authoritative guidance provides criteria for determining whether a cloud computing arrangement contains a software license that should be accounted for as internal-use software. The impact of this guidance on our financial statements is not expected to be material.
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.
	At March 31, 2015 and December 31, 2014, 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 MGE Energy's and MGE's long-term debt is based on quoted market prices for similar financial instruments at March 31, 2015 and December 31, 2014. 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.
	Derivatives include exchange-traded derivative contracts, over-the-counter transactions, a ten-year 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 classified as Level 3. Transactions done with an over-the-counter party are on inactive markets and are therefore considered unobservable and 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 ten-year purchased power agreement (see Footnote 9) was valued using an internally-developed 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, where such exchange-traded contracts exist, and upon calculations based on forward gas prices, where such exchange-traded contracts do not exist. 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.
	This model is prepared by members of MGE's Energy Accounting group. It is reviewed on a quarterly basis by management in Energy Supply and Finance to review the assumptions, inputs, and fair value measurements.
	The following table presents the significant unobservable inputs used in the pricing model.
			Model Input
		Significant Unobservable Inputs	31-Mar-15	31-Dec-14
		Basis adjustment:
		On peak	97.50%	98.10%
		Off peak	94.70%	95.00%
		Counterparty fuel mix:
		Internal generation	60% - 75%	50% - 70%
		Purchased power	40% - 25%	50% - 30%
	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 of MGE Energy and MGE. The notional investments earn interest based upon the semiannual rate of U.S. Treasury Bills having a 26 week maturity increased by 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.

Investment_in_ATC_Tables

Investment in ATC (Tables)	3 Months Ended
	Mar. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
ATC's Summarized Financial Data	For the three months ended March 31, 2015 and 2014, MGE Transco recorded the following:
				Three Months Ended
				March 31,
		(In thousands)		2015		2014
		Equity in earnings from investment in ATC	$	1,881	$	2,481
		Dividends received from ATC		1,420		1,917
		Capital contributions to ATC		178		533
	ATC's summarized financial data for the three months ended March 31, 2015 and 2014, is as follows:
				Three Months Ended
				March 31,
		(In thousands)		2015		2014
		Operating revenues	$	152,357	$	163,337
		Operating expenses		-79,951		-78,623
		Other income, net		62		388
		Interest expense, net		-24,483		-21,996
		Earnings before members' income taxes	$	47,985	$	63,106

Chattel_Paper_Agreements_Table

Chattel Paper Agreements (Tables)	3 Months Ended
	Mar. 31, 2015
Transfers and Servicing [Abstract]
Schedule of Remaining Contractual Maturities for Chattel Paper Agreements	As of March 31, 2015, the remaining contractual maturities of the chattel paper agreements were as follows:
		(In thousands)		2015		2016		2017		2018		Thereafter		Total
		Repurchase-to-Maturity Transactions:
		Loans	$	383	$	950	$	552	$	540	$	1,841	$	4,266

Pension_and_Other_Postretireme1

Pension and Other Postretirement Plans (Tables)	3 Months Ended
	Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Schedule of Net Periodic Benefit Costs	The following table presents the components of MGE Energy's and MGE's net periodic benefit costs recognized for the three months ended March 31, 2015 and 2014. A portion of the net periodic benefit cost is capitalized within the consolidated balance sheets.
				Three Months Ended
				March 31,
		(In thousands)		2015		2014
		Pension Benefits
		Components of net periodic cost (benefit):
		Service cost	$	1,798	$	1,484
		Interest cost		3,440		3,251
		Expected return on assets		-5,677		-5,279
		Amortization of:
		Prior service cost		6		49
		Actuarial loss		1,334		173
		Net periodic cost (benefit)	$	901	$	-322
		Postretirement Benefits
		Components of net periodic cost (benefit):
		Service cost	$	383	$	330
		Interest cost		778		772
		Expected return on assets		-703		-654
		Amortization of:
		Transition obligation		1		1
		Prior service benefit		-667		-668
		Actuarial loss		262		39
		Net periodic cost (benefit)	$	54	$	-180

Derivative_and_Hedging_Instrum1

Derivative and Hedging Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gross Notional Volume of Open Derivatives	The gross notional volume of open derivatives is as follows:
			31-Mar-15		31-Dec-14
		Commodity derivative contracts	408,920 MWh		448,000 MWh
		Commodity derivative contracts	2,785,000 Dth		4,405,000 Dth
		FTRs	691 MW		1,854 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 sheet. 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, MGE Energy and MGE have netted instruments with the same counterparty under a master netting agreement as well as the netting of collateral. At March 31, 2015, MGE Energy and MGE had the right to reclaim collateral (a receivable) of $0.6 million.
			Asset Derivatives				Liability Derivatives
	(In thousands)		Balance Sheet Location		Fair Value		Balance Sheet Location		Fair Value
	31-Mar-15
	Commodity derivative contracts		Other current assets	$	336		Derivative liability (current)	$	821
	Commodity derivative contracts		Other deferred charges		7		Derivative liability (long-term)		116
	FTRs		Other current assets		38		Derivative liability (current)		-
	Ten-year PPA		N/A		N/A		Derivative liability (current)		7,090
	Ten-year PPA		N/A		N/A		Derivative liability (long-term)		46,320
	31-Dec-14
	Commodity derivative contracts		Other current assets	$	130		Derivative liability (current)	$	2,262
	Commodity derivative contracts		Other deferred charges		93		Derivative liability (long-term)		171
	FTRs		Other current assets		642		Derivative liability (current)		-
	Ten-year PPA		N/A		N/A		Derivative liability (current)		6,870
	Ten-year PPA		N/A		N/A		Derivative liability (long-term)		46,560
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 sheet.
		Offsetting of Derivative Assets
		(In thousands)		Gross amounts		Gross amounts offset in balance sheet		Collateral posted against derivative positions		Net amount presented in balance sheet
		31-Mar-15
		Commodity derivative contracts	$	343	$	-343	$	-	$	-
		FTRs		38		-		-		38
		31-Dec-14
		Commodity derivative contracts	$	223	$	-223	$	-	$	-
		FTRs		642		-		-		642
Offsetting Liabilities		Offsetting of Derivative Liabilities
		(In thousands)		Gross amounts		Gross amounts offset in balance sheet		Collateral posted against derivative positions		Net amount presented in balance sheet
		31-Mar-15
		Commodity derivative contracts	$	937	$	-343	$	-565	$	29
		Ten-year PPA		53,410		-		-		53,410
		31-Dec-14
		Commodity derivative contracts	$	2,433	$	-223	$	-2,179	$	31
		Ten-year PPA		53,430		-		-		53,430
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 sheet at March 31, 2015 and 2014, and the consolidated income statement for the three months ended March 31, 2015 and 2014.
			2015					2014
	(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,	$	54,998	$	1,001		$	63,893	$	411
	Change in unrealized (loss) gain		1,318		-			-13,601		-
	Realized (loss) gain reclassified to a deferred account		-1,061		1,061			1,535		-1,535
	Realized gain (loss) reclassified to income
	statement		-1,289		-1,794			6,386		1,475
	Balance at March 31,	$	53,966	$	268		$	58,213	$	351
Derivative Gains and Losses in Income Statement			Realized losses (gains)
			2015					2014
	(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	$	420	$	1,761		$	-4,795	$	-1,220
	FTRs		-119		-			-636		-
	Ten-year PPA		1,021		-			-1,210		-

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Estimated Fair Market Value of Financial Instruments	The estimated fair market value of MGE Energy's and MGE's financial instruments are as follows:
				31-Mar-15					31-Dec-14
		(In thousands)		Carrying Amount		Fair Value			Carrying Amount		Fair Value
		MGE Energy
		Assets:
		Cash and cash equivalents	$	70,703	$	70,703		$	65,755	$	65,755
		Liabilities:
		Short-term debt - commercial paper		-		-			7,000		7,000
		Long-term debt*		398,653		465,534			399,690		457,420
		MGE
		Assets:
		Cash and cash equivalents	$	17,156	$	17,156		$	4,562	$	4,562
		Liabilities:
		Short-term debt - commercial paper		-		-			7,000		7,000
		Long-term debt*		398,653		465,534			399,690		457,420
		*Includes long-term debt due within one year.
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 for MGE Energy and MGE.
				Fair Value as of March 31, 2015
		(In thousands)		Total		Level 1		Level 2		Level 3
		MGE Energy
		Assets:
		Derivatives, net	$	38	$	-	$	-	$	38
		Exchange-traded investments		786		786		-		-
		Total Assets	$	824	$	786	$	-	$	38
		Liabilities:
		Derivatives, net(a)	$	54,004	$	100	$	-	$	53,904
		Deferred compensation		2,958		-		2,958		-
		Total Liabilities	$	56,962	$	100	$	2,958	$	53,904
		MGE
		Assets:
		Derivatives, net	$	38	$	-	$	-	$	38
		Exchange-traded investments		214		214		-		-
		Total Assets	$	252	$	214	$	-	$	38
		Liabilities:
		Derivatives, net(a)	$	54,004	$	100	$	-	$	53,904
		Deferred compensation		2,958		-		2,958		-
		Total Liabilities	$	56,962	$	100	$	2,958	$	53,904
				Fair Value as of December 31, 2014
		(In thousands)		Total		Level 1		Level 2		Level 3
		MGE Energy
		Assets:
		Derivatives, net	$	642	$	-	$	-	$	642
		Exchange-traded investments		927		927		-		-
		Total Assets	$	1,569	$	927	$	-	$	642
		Liabilities:
		Derivatives, net(a)	$	55,640	$	1,012	$	-	$	54,628
		Deferred compensation		2,832		-		2,832		-
		Total Liabilities	$	58,472	$	1,012	$	2,832	$	54,628
		MGE
		Assets:
		Derivatives, net	$	642	$	-	$	-	$	642
		Exchange-traded investments		350		350		-		-
		Total Assets	$	992	$	350	$	-	$	642
		Liabilities:
		Derivatives, net(a)	$	55,640	$	1,012	$	-	$	54,628
		Deferred compensation		2,832		-		2,832		-
		Total Liabilities	$	58,472	$	1,012	$	2,832	$	54,628
		(a) These amounts are shown gross and exclude $0.6 million and $2.2 million of collateral that was
		posted against derivative positions with counterparties as of March 31, 2015 and
		December 31, 2014, respectively.
Significant Unobservable Inputs	The following table presents the significant unobservable inputs used in the pricing model.
				Model Input
		Significant Unobservable Inputs		31-Mar-15		31-Dec-14
		Basis adjustment:
		On peak		97.50%		98.10%
		Off peak		94.70%		95.00%
		Counterparty fuel mix:
		Internal generation		60% - 75%		50% - 70%
		Purchased power		40% - 25%		50% - 30%
Changes in Level 3 Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following table summarizes the changes in Level 3 assets and liabilities measured at fair value on a recurring basis for both MGE Energy and MGE.
				Three Months Ended
				March 31,
		(In thousands)		2015		2014
		Beginning balance	$	-53,986	$	-64,628
		Realized and unrealized gains (losses):
		Included in regulatory liabilities		119		5,831
		Included in other comprehensive income		-		-
		Included in earnings		-1,328		6,634
		Included in current assets		-		-53
		Purchases		6,162		6,859
		Sales		34		-60
		Issuances		-		-
		Settlements		-4,867		-13,380
		Transfers in and/or out of Level 3		-		-
		Balance as of March 31,	$	-53,866	$	-58,797
		Total gains (losses) included in earnings attributed to the change in unrealized gains (losses) related to assets and liabilities held at March 31,(b)	$	-	$	-
	(b) MGE's exchange-traded derivative contracts, over-the-counter party transactions, ten-year 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 for both MGE Energy and MGE (b).
				Three Months Ended
				March 31,
		(In thousands)		2015		2014
		Purchased Power Expense	$	-1,328	$	6,634
	(b) MGE's exchange-traded derivative contracts, over-the-counter party transactions, ten-year 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.

Segment_Information_Tables

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2015
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		Non- Regulated Energy		Transmission Investment		All Others		Consolidation/ Elimination Entries		Consolidated Total
	Three Months Ended March 31, 2015
	Operating revenues	$	98,240	$	69,928	$	1,966	$	-	$	-	$	-	$	170,134
	Interdepartmental revenues		115		2,725		9,847		-		-		-12,687		-
	Total operating revenues		98,355		72,653		11,813		-		-		-12,687		170,134
	Depreciation and amortization		-7,332		-1,642		-1,863		-		-12		-		-10,849
	Other operating expenses		-79,800		-60,068		-50		-		-203		12,687		-127,434
	Operating income (loss)		11,223		10,943		9,900		-		-215		-		31,851
	Other (deductions) income, net		90		-1		-		1,881		135		-		2,105
	Interest (expense) income, net		-2,819		-804		-1,518		-		50		-		-5,091
	Income (loss) before taxes		8,494		10,138		8,382		1,881		-30		-		28,865
	Income tax provision		-2,383		-4,081		-3,364		-756		-3		-		-10,587
	Net income (loss)	$	6,111	$	6,057	$	5,018	$	1,125	$	-33	$	-	$	18,278
	Three Months Ended March 31, 2014
	Operating revenues	$	98,852	$	110,713	$	680	$	-	$	-	$	-	$	210,245
	Interdepartmental revenues		118		3,624		10,670		-		-		-14,412		-
	Total operating revenues		98,970		114,337		11,350		-		-		-14,412		210,245
	Depreciation and amortization		-6,337		-1,563		-1,834		-		-12		-		-9,746
	Other operating expenses		-77,901		-92,843		-40		-		-156		14,412		-156,528
	Operating income (loss)		14,732		19,931		9,476		-		-168		-		43,971
	Other (deductions) income, net		1,827		-35		-		2,481		279		-		4,552
	Interest (expense) income, net		-2,205		-804		-1,572		-		40		-		-4,541
	Income before taxes		14,354		19,092		7,904		2,481		151		-		43,982
	Income tax provision		-4,353		-7,665		-3,172		-998		-77		-		-16,265
	Net income	$	10,001	$	11,427	$	4,732	$	1,483	$	74	$	-	$	27,717
	The following tables show segment information for MGE's operations for the indicated periods:
	(In thousands)MGE		Electric		Gas		Non- Regulated Energy		Transmission Investment		Consolidation/ Elimination Entries		Consolidated Total
	Three Months Ended March 31, 2015
	Operating revenues	$	98,245	$	69,933	$	1,966	$	-	$	-	$	170,144
	Interdepartmental revenues		110		2,720		9,847		-		-12,677		-
	Total operating revenues		98,355		72,653		11,813		-		-12,677		170,144
	Depreciation and amortization		-7,332		-1,642		-1,863		-		-		-10,837
	Other operating expenses*		-82,142		-64,138		-3,414		-		12,677		-137,017
	Operating income*		8,881		6,873		6,536		-		-		22,290
	Other (deductions) income, net*		49		-12		-		1,125		-		1,162
	Interest expense, net		-2,819		-804		-1,518		-		-		-5,141
	Net income		6,111		6,057		5,018		1,125		-		18,311
	Less: Net income attributable to
	noncontrolling interest, net of tax		-		-		-		-		-6,553		-6,553
	Net income attributable to MGE	$	6,111	$	6,057	$	5,018	$	1,125	$	-6,553	$	11,758
	Three Months Ended March 31, 2014
	Operating revenues	$	98,858	$	110,718	$	680	$	-	$	-	$	210,256
	Interdepartmental revenues		112		3,619		10,670		-		-14,401		-
	Total operating revenues		98,970		114,337		11,350		-		-14,401		210,256
	Depreciation and amortization		-6,337		-1,563		-1,834		-		-		-9,734
	Other operating expenses*		-82,046		-100,450		-3,212		-		14,401		-171,307
	Operating income*		10,587		12,324		6,304		-		-		29,215
	Other (deductions) income, net*		1,619		-93		-		1,483		-		3,009
	Interest expense, net		-2,205		-804		-1,572		-		-		-4,581
	Net income		10,001		11,427		4,732		1,483		-		27,643
	Less: Net income attributable to
	noncontrolling interest, net of tax		-		-		-		-		-6,510		-6,510
	Net income attributable to MGE	$	10,001	$	11,427	$	4,732	$	1,483	$	-6,510	$	21,133
	*Amounts are shown net of the related tax expense, consistent with the presentation on the consolidated MGE Income Statement.

Equity_and_Financing_Arrangeme1

Equity and Financing Arrangements (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Common Stock [Abstract]
Common stock issued during period	0	0
Dilutive Shares Calculation [Abstract]
Dilutive securities	$0

Investment_in_ATC_Details1

Investment in ATC (Details-1) (USD $)	3 Months Ended		0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Apr. 30, 2015	Dec. 31, 2014
Schedule Of Equity Method Investments [Line Items]
Equity earnings from investment	$1,881,000	$2,481,000
Dividend income from investment	1,420,000	1,917,000
Capital contributions to investment	280,000	693,000
MGE Transco [Member] | ATC [Member]
Schedule Of Equity Method Investments [Line Items]
Equity earnings from investment	1,881,000	2,481,000
Dividend income from investment	1,420,000	1,917,000
Capital contributions to investment	178,000	533,000
Equity method investment	68,300,000			67,700,000
MGE Transco [Member] | ATC [Member] | Subsequent Event [Member]
Schedule Of Equity Method Investments [Line Items]
Capital contributions to investment			$200,000

Investment_in_ATC_Details2

Investment in ATC (Details-2) (ATC [Member], USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
ATC [Member]
Schedule Of Equity Method Investments [Line Items]
Operating revenues	$152,357	$163,337
Operating expenses	-79,951	-78,623
Other income, net	62	388
Interest expense, net	-24,483	-21,996
Earnings before members' income taxes	$47,985	$63,106

Chattel_Paper_Agreements_Detai

Chattel Paper Agreements (Details-1) (USD $)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Cumulative effect of new accounting guidance, retained earnings		($142,000)
Chattel Paper Agreements [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreement, maximum exposure	10,000,000
Repurchase-to-Maturity Transactions, loans due	4,266,000
Cumulative effect of new accounting guidance, retained earnings		-100,000
2015 [Member] | Chattel Paper Agreements [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase-to-Maturity Transactions, loans due	383,000
2016 [Member] | Chattel Paper Agreements [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase-to-Maturity Transactions, loans due	950,000
2017 [Member] | Chattel Paper Agreements [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase-to-Maturity Transactions, loans due	552,000
2018 [Member] | Chattel Paper Agreements [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase-to-Maturity Transactions, loans due	540,000
Thereafter [Member] | Chattel Paper Agreements [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase-to-Maturity Transactions, loans due	1,841,000
Minimum [Member] | Chattel Paper Agreements [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
MGE guarantee to the financial institution, term	1 year
Maximum [Member] | Chattel Paper Agreements [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
MGE guarantee to the financial institution, term	10 years

Taxes_Details

Taxes (Details)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Income Tax Disclosure [Line Items]
Effective income tax rate	36.70%	37.00%
MGE [Member]
Income Tax Disclosure [Line Items]
Effective income tax rate	36.60%	36.90%

Pension_and_Other_Postretireme2

Pension and Other Postretirement Plans (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Pension Benefits [Member]
Components of net periodic cost (benefit):
Service cost	$1,798	$1,484
Interest cost	3,440	3,251
Expected return on assets	-5,677	-5,279
Amortization of:
Prior service (benefit) cost	6	49
Actuarial loss	1,334	173
Net periodic cost (benefit)	901	-322
Postretirement Benefits [Member]
Components of net periodic cost (benefit):
Service cost	383	330
Interest cost	778	772
Expected return on assets	-703	-654
Amortization of:
Transition obligation	1	1
Prior service (benefit) cost	-667	-668
Actuarial loss	262	39
Net periodic cost (benefit)	$54	($180)

Share_Based_Compensation_Detai

Share Based Compensation (Details) (Performance Units [Member], USD $)	3 Months Ended		0 Months Ended	1 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Feb. 20, 2015	Jan. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$0.50	$0.80
Cash payments distributed related to awards previously granted and now payable				1.3
Awards forfeited during period, value	0.2	0
Awards forfeited during period, units	4,676	0
Outstanding awards vested during period	$5.30
Performance Unit Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted during period (in units)			18,948
Award vesting period	5 years
Director Incentive Agreement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted during period (in units)				3,794
Award vesting period	3 years

Commitments_and_Contingencies_

Commitments and Contingencies (Details-1) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015
	ppb
	MW
Columbia Environmental Project, SCR [Member] | MGE [Member]
Columbia Commitments
Share of projected project cost, minimum	30
Share of projected project cost, maximum	40
EPA [Member] | Legal Entity Type of Counterparty [Domain]
Effluent Limitations Guidelines and Standards for Steam Electric Power Generating Source Category [Abstract]
Proposed air pollution control and ash handling systems capacity at coal burning power plants, minimum (in MW)	50
EPA's Greenhouse Gas Reduction Guidelines
National average reduction of greenhouse gas emissions by the year 2030, percentage	30.00%
Wisconsin state average reduction goal of greenhouse gas emissions by the year 2030, percentage	34.00%
Compliance plan preparation term related to the greenhouse gas emissions reduction guidelines once the final rule is approved in 2015	2 years
Ozone NAAQS
Proposed lowered regulated level of Ozone NAAQS, minimum (in parts per billion)	65
Proposed lowered regulated level of Ozone NAAQS, maximum (in parts per billion)	70
Current regulated level of Ozone NAAQS (in parts per billion)	75
Proposed lowered regulated level of Ozone NAAQS, potential additional minimum (in parts per billion)	60
EPA's Coal Combustion Residuals Rule
Federal Register publication waiting period to become effective, term	6 months

Derivative_and_Hedging_Instrum2

Derivative and Hedging Instruments (Details-1) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
	Dth	Dth
	MWh	MWh
Gross Notional Volume of Open Derivatives
Derivative, right to reclaim collateral (receivable)	$600,000
Other Current Assets [Member]
Derivative fair values [Abstract]
Derivative fair value, net	268,000	1,001,000	351,000	411,000
Commodity Contracts And Financial Transimission Rights [Member]
Derivative fair values [Abstract]
Derivative fair value, net	-600,000	-1,600,000
Commodity Derivative Contracts [Member]
Gross Notional Volume of Open Derivatives
Notional amount, energy measure (in MWh)	408,920	448,000
Notional amount, decatherm measure (in Dth)	2,785,000	4,405,000
Derivative fair values [Abstract]
Asset Derivatives, fair value, gross basis	343,000	223,000
Liability Derivatives, fair value, gross basis	937,000	2,433,000
Commodity Derivative Contracts [Member] | Other Current Assets [Member]
Derivative fair values [Abstract]
Asset Derivatives, fair value, gross basis	336,000	130,000
Commodity Derivative Contracts [Member] | Other Deferred Charges [Member]
Derivative fair values [Abstract]
Asset Derivatives, fair value, gross basis	7,000	93,000
Commodity Derivative Contracts [Member] | Derivative Liability (Current) [Member]
Derivative fair values [Abstract]
Liability Derivatives, fair value, gross basis	821,000	2,262,000
Commodity Derivative Contracts [Member] | Derivative Liability (Long-term) [Member]
Derivative fair values [Abstract]
Liability Derivatives, fair value, gross basis	116,000	171,000
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)	691	1,854
Derivative fair values [Abstract]
Asset Derivatives, fair value, gross basis	38,000	642,000
Financial Transmission Rights [Member] | Other Current Assets [Member]
Derivative fair values [Abstract]
Asset Derivatives, fair value, gross basis	38,000	642,000
Financial Transmission Rights [Member] | Derivative Liability (Current) [Member]
Derivative fair values [Abstract]
Liability Derivatives, fair value, gross basis	0	0
Ten-year PPA [Member]
Derivative fair values [Abstract]
Derivative fair value, net	-53,400,000	-53,400,000
Liability Derivatives, fair value, gross basis	53,410,000	53,430,000
Ten-year PPA [Member] | Derivative Liability (Current) [Member]
Derivative fair values [Abstract]
Liability Derivatives, fair value, gross basis	7,090,000	6,870,000
Ten-year PPA [Member] | Derivative Liability (Long-term) [Member]
Derivative fair values [Abstract]
Liability Derivatives, fair value, gross basis	$46,320,000	$46,560,000

Derivative_and_Hedging_Instrum3

Derivative and Hedging Instruments (Details-2) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Commodity Derivative Contracts [Member]
Offsetting Assets [Line Items]
Gross amounts	$343	$223
Gross amounts offset in balance sheet	-343	-223
Collateral posted against derivative positions	0	0
Net amount presented in balance sheet	0	0
Financial Transmission Rights [Member]
Offsetting Assets [Line Items]
Gross amounts	38	642
Gross amounts offset in balance sheet	0	0
Collateral posted against derivative positions	0	0
Net amount presented in balance sheet	$38	$642

Derivative_and_Hedging_Instrum4

Derivative and Hedging Instruments (Details-3) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Offsetting Liabilities [Line Items]
Collateral posted against derivative positions	($600)	($2,200)
Commodity Derivative Contracts [Member]
Offsetting Liabilities [Line Items]
Gross amounts	937	2,433
Gross amounts offset in balance sheet	-343	-223
Collateral posted against derivative positions	-565	-2,179
Net amount presented in balance sheet	29	31
Purchased Power Agreement [Member]
Offsetting Liabilities [Line Items]
Gross amounts	53,410	53,430
Gross amounts offset in balance sheet	0	0
Collateral posted against derivative positions	0	0
Net amount presented in balance sheet	$53,410	$53,430

Derivative_and_Hedging_Instrum5

Derivative and Hedging Instruments (Details-4) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Regulatory Asset [Member]
Change In Derivative Fair Value [Roll Forward]
Beginning balance,	$54,998	$63,893
Change in unrealized loss (gain)	1,318	-13,601
Realized gain (loss) reclassified to a deferred account	-1,061	1,535
Realized gain (loss) reclassified to income statement	-1,289	6,386
Ending balance,	53,966	58,213
Other Current Assets [Member]
Change In Derivative Fair Value [Roll Forward]
Beginning balance,	1,001	411
Change in unrealized loss (gain)	0	0
Realized gain (loss) reclassified to a deferred account	1,061	-1,535
Realized gain (loss) reclassified to income statement	-1,794	1,475
Ending balance,	$268	$351

Derivative_and_Hedging_Instrum6

Derivative and Hedging Instruments (Details-5) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Counterparties in net liability position or default [Abstract]
Derivative, net liability position of counterparties (less than $0.1 million)	$100,000		$100,000
Number of counterparties in default	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	420,000	-4,795,000
Commodity Derivative Contracts [Member] | Cost Of Gas Sold Expense [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	1,761,000	-1,220,000
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	-119,000	-636,000
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 ten-year 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	1,021,000	-1,210,000
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

Rate_Matters_Details

Rate Matters (Details) (USD $)	3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
MGE [Member]
Purchased Gas Adjustment [Abstract]
Purchased gas adjustment, overcollection	6.7	1.2
PSCW [Member] | Legal Entity Type of Counterparty [Domain]
Fuel Rules [Abstract]
Fuel rules, bandwidth	2.00%
Fuel rules, electric fuel deferred costs upper threshold	102.00%
Fuel rules, electric fuel deferred costs lower threshold	98.00%
PSCW [Member] | MGE [Member]
Rate Proceedings [Abstract]
Authorized return on equity, percentage	10.20%	10.30%
Fuel Rules [Abstract]
Fuel rules, deferred electric cost	2.4
PSCW [Member] | MGE [Member] | Fuel Rules Surplus Credit, 2012 [Member]
Rate Proceedings [Abstract]
Return of electric fuel credit, total		6.3
Fuel Rules [Abstract]
Return of electric fuel credit, current period			1.6
PSCW [Member] | Columbia Environmental Project [Member] | MGE [Member]
Rate Proceedings [Abstract]
Authorized AFUDC Rate		100.00%
Electric [Member] | PSCW [Member] | MGE [Member]
Rate Proceedings [Abstract]
Authorized rate increase (decrease), percentage	3.80%	0.00%
Authorized rate increase (decrease), amount	15.4	0
Gas [Member] | PSCW [Member] | MGE [Member]
Rate Proceedings [Abstract]
Authorized rate increase (decrease), percentage	-2.00%	0.00%
Authorized rate increase (decrease), amount	-3.8	0

Fair_Value_of_Financial_Instru2

Fair Value of Financial Instruments (Details-1) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Thousands, unless otherwise specified
Carrying Amount [Member]
Assets:
Cash and cash equivalents	$70,703		$65,755
Liabilities:
Short-term debt - commercial paper	0		7,000
Long-term debt	398,653	[1]	399,690	[1]
Fair Value [Member]
Assets:
Cash and cash equivalents	70,703		65,755
Liabilities:
Short-term debt - commercial paper	0		7,000
Long-term debt	465,534	[1]	457,420	[1]
MGE [Member] | Carrying Amount [Member]
Assets:
Cash and cash equivalents	17,156		4,562
Liabilities:
Short-term debt - commercial paper	0		7,000
Long-term debt	398,653	[1]	399,690	[1]
MGE [Member] | Fair Value [Member]
Assets:
Cash and cash equivalents	17,156		4,562
Liabilities:
Short-term debt - commercial paper	0		7,000
Long-term debt	$465,534	[1]	$457,420	[1]
[1]	*Includes long-term debt due within one year.

Fair_Value_of_Financial_Instru3

Fair Value of Financial Instruments (Details-2) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Thousands, unless otherwise specified
Liabilities:
Derivative liability, collateral offset	$600		$2,200
Recurring [Member]
Assets:
Derivative assets, net	38		642
Total Assets	824		1,569
Liabilities:
Derivative liabilities, net	54,004	[1]	55,640	[1]
Deferred compensation	2,958		2,832
Total liabilities	56,962		58,472
Recurring [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	786		927
Recurring [Member] | Level 1 [Member]
Assets:
Derivative assets, net	0		0
Total Assets	786		927
Liabilities:
Derivative liabilities, net	100	[1]	1,012	[1]
Deferred compensation	0		0
Total liabilities	100		1,012
Recurring [Member] | Level 1 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	786		927
Recurring [Member] | Level 2 [Member]
Assets:
Derivative assets, net	0		0
Total Assets	0		0
Liabilities:
Derivative liabilities, net	0	[1]	0	[1]
Deferred compensation	2,958		2,832
Total liabilities	2,958		2,832
Recurring [Member] | Level 2 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	0		0
Recurring [Member] | Level 3 [Member]
Assets:
Derivative assets, net	38		642
Total Assets	38		642
Liabilities:
Derivative liabilities, net	53,904	[1]	54,628	[1]
Deferred compensation	0		0
Total liabilities	53,904		54,628
Recurring [Member] | Level 3 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	0		0
MGE [Member]
Liabilities:
Derivative liability, collateral offset	600		2,200
MGE [Member] | Recurring [Member]
Assets:
Derivative assets, net	38		642
Total Assets	252		992
Liabilities:
Derivative liabilities, net	54,004	[1]	55,640	[1]
Deferred compensation	2,958		2,832
Total liabilities	56,962		58,472
MGE [Member] | Recurring [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	214		350
MGE [Member] | Recurring [Member] | Level 1 [Member]
Assets:
Derivative assets, net	0		0
Total Assets	214		350
Liabilities:
Derivative liabilities, net	100	[1]	1,012	[1]
Deferred compensation	0		0
Total liabilities	100		1,012
MGE [Member] | Recurring [Member] | Level 1 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	214		350
MGE [Member] | Recurring [Member] | Level 2 [Member]
Assets:
Derivative assets, net	0		0
Total Assets	0		0
Liabilities:
Derivative liabilities, net	0	[1]	0	[1]
Deferred compensation	2,958		2,832
Total liabilities	2,958		2,832
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:
Derivative assets, net	38		642
Total Assets	38		642
Liabilities:
Derivative liabilities, net	53,904	[1]	54,628	[1]
Deferred compensation	0		0
Total liabilities	53,904		54,628
MGE [Member] | Recurring [Member] | Level 3 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	$0		$0
[1]	These amounts are shown gross and exclude $0.6 and $2.2 million of collateral that was posted against derivative positions with counterparties as of March 31, 2014 and December 31, 2014, respectively.

Fair_Value_of_Financial_Instru4

Fair Value of Financial Instruments (Details-3)	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Fair Value Inputs Assets Quantitative Information [Line Items]
Basis adjustment - on peak	97.50%	98.10%
Basis adjustment - off peak	94.70%	95.00%
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 [Abstract]
Internal generation	60.00%	50.00%
Purchased power	40.00%	50.00%
Maximum [Member]
Counterparty fuel mix [Abstract]
Internal generation	75.00%	70.00%
Purchased power	25.00%	30.00%

Fair_Value_of_Financial_Instru5

Fair Value of Financial Instruments (Details-4) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance,	($53,986)		($64,628)
Realized and unrealized gains (losses):
Included in regulatory liabilities (assets)	119		5,831
Included in other comprehensive income	0		0
Included in earnings	-1,328	[1]	6,634	[1]
Included in current assets	0		-53
Purchases	6,162		6,859
Sales	34		-60
Issuances	0		0
Settlements	-4,867		-13,380
Transfers in and/or out of level 3	0		0
Ending balance,	-53,866		-58,797
Total gains (losses) included in earnings attributed to the change in unrealized gains (losses) related to assets and liabilities	0	[1]	0	[1]
Purchased Power Expense [Member]
Realized and unrealized gains (losses):
Included in earnings	($1,328)	[1]	$6,634	[1]
[1]	MGE's exchange-traded derivative contracts, over-the-counter party transactions, ten-year 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.

Segment_Information_Details

Segment Information (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Segment Reporting Information [Line Items]
Operating revenues	$170,134		$210,245
Depreciation and amortization	-10,849		-9,746
Other operating expenses	-127,434		-156,528
Operating Income	31,851		43,971
Other income (deductions), net	2,105		4,552
Interest (expense) income, net	-5,091		-4,541
Income before income taxes	28,865		43,982
Income tax (provision) benefit	-10,587		-16,265
Net Income (Loss)	18,278		27,717
Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	98,240		98,852
Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	69,928		110,713
Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,966		680
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	170,134		210,245
Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	98,355		98,970
Depreciation and amortization	-7,332		-6,337
Other operating expenses	-79,800		-77,901
Operating Income	11,223		14,732
Other income (deductions), net	90		1,827
Interest (expense) income, net	-2,819		-2,205
Income before income taxes	8,494		14,354
Income tax (provision) benefit	-2,383		-4,353
Net Income (Loss)	6,111		10,001
Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	72,653		114,337
Depreciation and amortization	-1,642		-1,563
Other operating expenses	-60,068		-92,843
Operating Income	10,943		19,931
Other income (deductions), net	-1		-35
Interest (expense) income, net	-804		-804
Income before income taxes	10,138		19,092
Income tax (provision) benefit	-4,081		-7,665
Net Income (Loss)	6,057		11,427
Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	11,813		11,350
Depreciation and amortization	-1,863		-1,834
Other operating expenses	-50		-40
Operating Income	9,900		9,476
Other income (deductions), net	0		0
Interest (expense) income, net	-1,518		-1,572
Income before income taxes	8,382		7,904
Income tax (provision) benefit	-3,364		-3,172
Net Income (Loss)	5,018		4,732
Operating Segments [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues	0		0
Depreciation and amortization	0		0
Other operating expenses	0		0
Operating Income	0		0
Other income (deductions), net	1,881		2,481
Interest (expense) income, net	0		0
Income before income taxes	1,881		2,481
Income tax (provision) benefit	-756		-998
Net Income (Loss)	1,125		1,483
Operating Segments [Member] | All Others [Member]
Segment Reporting Information [Line Items]
Operating revenues	0		0
Depreciation and amortization	-12		-12
Other operating expenses	-203		-156
Operating Income	-215		-168
Other income (deductions), net	135		279
Interest (expense) income, net	50		40
Income before income taxes	-30		151
Income tax (provision) benefit	-3		-77
Net Income (Loss)	-33		74
Consolidation Elimination Entries [Member]
Segment Reporting Information [Line Items]
Operating revenues	-12,687		-14,412
Depreciation and amortization	0		0
Other operating expenses	12,687		14,412
Operating Income	0		0
Other income (deductions), net	0		0
Interest (expense) income, net	0		0
Income before income taxes	0		0
Income tax (provision) benefit	0		0
Net Income (Loss)	0		0
Consolidation Elimination Entries [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	115		118
Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	2,725		3,624
Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	9,847		10,670
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	170,144		210,256
Depreciation and amortization	-10,837		-9,734
Other operating expenses	-137,017	[1]	-171,307	[1]
Operating Income	22,290	[1]	29,215	[1]
Other income (deductions), net	1,162	[1]	3,009	[1]
Interest (expense) income, net	-5,141		-4,581
Income tax (provision) benefit	-9,776		-14,924
Net Income Including Noncontrolling Interest	18,311		27,643
Less Net Income Attributable to Noncontrolling Interest, net of tax	-6,553		-6,510
Net Income (Loss)	11,758		21,133
MGE [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	98,245		98,858
MGE [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	69,933		110,718
MGE [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,966		680
MGE [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues	0		0
MGE [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	170,144		210,256
MGE [Member] | Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	98,355		98,970
Depreciation and amortization	-7,332		-6,337
Other operating expenses	-82,142	[1]	-82,046	[1]
Operating Income	8,881	[1]	10,587	[1]
Other income (deductions), net	49	[1]	1,619	[1]
Interest (expense) income, net	-2,819		-2,205
Net Income Including Noncontrolling Interest	6,111		10,001
Less Net Income Attributable to Noncontrolling Interest, net of tax	0		0
Net Income (Loss)	6,111		10,001
MGE [Member] | Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	72,653		114,337
Depreciation and amortization	-1,642		-1,563
Other operating expenses	-64,138	[1]	-100,450	[1]
Operating Income	6,873	[1]	12,324	[1]
Other income (deductions), net	-12	[1]	-93	[1]
Interest (expense) income, net	-804		-804
Net Income Including Noncontrolling Interest	6,057		11,427
Less Net Income Attributable to Noncontrolling Interest, net of tax	0		0
Net Income (Loss)	6,057		11,427
MGE [Member] | Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	11,813		11,350
Depreciation and amortization	-1,863		-1,834
Other operating expenses	-3,414	[1]	-3,212	[1]
Operating Income	6,536	[1]	6,304	[1]
Other income (deductions), net	0	[1]	0	[1]
Interest (expense) income, net	-1,518		-1,572
Net Income Including Noncontrolling Interest	5,018		4,732
Less Net Income Attributable to Noncontrolling Interest, net of tax	0		0
Net Income (Loss)	5,018		4,732
MGE [Member] | Operating Segments [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues	0		0
Depreciation and amortization	0		0
Other operating expenses	0	[1]	0	[1]
Operating Income	0	[1]	0	[1]
Other income (deductions), net	1,125	[1]	1,483	[1]
Interest (expense) income, net	0		0
Net Income Including Noncontrolling Interest	1,125		1,483
Less Net Income Attributable to Noncontrolling Interest, net of tax	0		0
Net Income (Loss)	1,125		1,483
MGE [Member] | Consolidation Elimination Entries [Member]
Segment Reporting Information [Line Items]
Operating revenues	-12,677		-14,401
Depreciation and amortization	0		0
Other operating expenses	12,677	[1]	14,401	[1]
Operating Income	0	[1]	0	[1]
Other income (deductions), net	0	[1]	0	[1]
Interest (expense) income, net	0		0
Net Income Including Noncontrolling Interest	0		0
Less Net Income Attributable to Noncontrolling Interest, net of tax	-6,553		-6,510
Net Income (Loss)	-6,553		-6,510
MGE [Member] | Consolidation Elimination Entries [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	110		112
MGE [Member] | Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	2,720		3,619
MGE [Member] | Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	9,847		10,670
MGE [Member] | Consolidation Elimination Entries [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues	$0		$0
[1]	*Amounts are shown net of the related tax expense, consistent with the presentation on the consolidated MGE Income Statement.