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Pursuant to the provisions of the rate order, the fuel rules bandwidth will be plus or minus this percentage.

+ References

No definition available.

+ Details

Name:	mgee_FuelRulesBandwidth
Namespace Prefix:	mgee_
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- Definition

Under fuel rules, the amount in which an entity is required to defer the benefit of lower costs if actual electric fuel costs were less than the allowed electric fuel costs in latest rate order.

+ References

No definition available.

+ Details

Name:	mgee_FuelRulesElectricFuelCostsDeferralLowerThreshold
Namespace Prefix:	mgee_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Under fuel rules, the amount in which an entity would defer if actual electric fuel costs exceeded allowed electric fuel costs in latest rate order.

+ References

No definition available.

+ Details

Name:	mgee_FuelRulesElectricFuelCostsDeferralUpperThreshold
Namespace Prefix:	mgee_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The fuel rules credit that is not required to be refunded to customers and will be amortized. The fuel credit will accrue interest at weighted cost of capital.

+ References

No definition available.

+ Details

Name:	mgee_PublicUtilitiesReturnOfFuelRulesCredit
Namespace Prefix:	mgee_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective rate, including composite rate, of cost of financing additions to qualifying regulated assets, commonly called allowance for funds used during construction.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 835

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6501662&loc=d3e56162-110433

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 835

-Section 25

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6501569&loc=d3e55921-110430

+ Details

Name:	us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of public utility's approved rate increase (decrease) by regulatory agency.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage of public utility's approved rate increase (decrease) by regulatory agency.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesApprovedRateIncreaseDecreasePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of public utility's approved return on equity.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesApprovedReturnOnEquityPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_PublicUtilitiesRateMattersAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=mgee_ElectricRateProceedingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=mgee_GasRateProceedingMember
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Rate Matters (Details) (PSCW [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2015	Oct. 31, 2014
Public Utilities, Rate Matters [Abstract]
Authorized AFUDC rate	50.00%	50.00%	50.00%
MGE [Member]
Public Utilities, Rate Matters [Abstract]
Authorized return on common stock	10.30%	10.30%
Fuel Rules [Abstract]
Fuel rules, bandwidth	2.00%
Fuel rules, electric fuel costs, deferral, upper threshold	102.00%
Fuel rules, electric fuel costs, deferral, lower threshold	98.00%
Fuel Rules Credit, 2012 [Member] \| MGE [Member]
Public Utilities, Rate Matters [Abstract]
Return of electric fuel credit, total	6.3
Fuel Rules Credit, 2013 [Member] \| MGE [Member]
Public Utilities, Rate Matters [Abstract]
Return of electric fuel credit, total					6.5
Approved Future Rate Matters [Member] \| MGE [Member]
Public Utilities, Rate Matters [Abstract]
Authorized return on common stock				10.20%
Columbia Environmental Project [Member]
Public Utilities, Rate Matters [Abstract]
Authorized AFUDC rate	100.00%	50.00%	100.00%
Columbia Environmental Project [Member] \| MGE [Member]
Public Utilities, Rate Matters [Abstract]
Authorized AFUDC rate	100.00%	50.00%
Electric Rate Proceeding [Member] \| MGE [Member]
Public Utilities, Rate Matters [Abstract]
Authorized rate increase (decrease), percentage	0.00%	3.80%	4.30%
Authorized rate increase (decrease), amount	0	14.9	15.7
Electric Rate Proceeding [Member] \| Approved Future Rate Matters [Member] \| MGE [Member]
Public Utilities, Rate Matters [Abstract]
Authorized rate increase (decrease), percentage				3.80%
Authorized rate increase (decrease), amount				15.4
Gas Rate Proceeding [Member] \| MGE [Member]
Public Utilities, Rate Matters [Abstract]
Authorized rate increase (decrease), percentage	0.00%	1.00%	0.30%
Authorized rate increase (decrease), amount	0	1.6	0.6
Gas Rate Proceeding [Member] \| Approved Future Rate Matters [Member] \| MGE [Member]
Public Utilities, Rate Matters [Abstract]
Authorized rate increase (decrease), percentage				(2.00%)
Authorized rate increase (decrease), amount				(3.8)