XML 26 R37.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Columbia Environmental Project Construction (Details) (USD $) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2013 | Mar. 31, 2012 | Dec. 31, 2012
Expected Capital Expenditures [Line Items] |  |  |
Total incurred costs to date | $ 115,803,000 |  | 98,411,000
MGE rate of return | 50.00% |  |
Columbia Environmental Project [Member] |  |  |
Expected Capital Expenditures [Line Items] |  |  |
MGE's share of expected capital expenditures | 140,000,000 |  |
Total incurred costs to date | 78,800,000 |  |
Carrying cost on pre-construction costs - AFUDC rate | 50.00% |  | 100.00%
AFUDC - equity funds | 500,000 | 100,000 |
Columbia Environmental Project [Member] | One Year From Balance Sheet Date [Member] |  |  |
Expected Capital Expenditures [Line Items] |  |  |
MGE's share of expected capital expenditures | 49,000,000 |  |
Columbia Environmental Project [Member] | More Than One And Within Two Years From Balance Sheet Date [Member] |  |  |
Expected Capital Expenditures [Line Items] |  |  |
MGE's share of expected capital expenditures | $ 12,000,000 |  |
Columbia Units [Member] |  |  |
Columbia Units [Line Items] |  |  |
Columbia's share of MGE's net generating capability | 29.00% |  |
Ownership interest in jointly owned plant | 22.00% |  |
WPL ownership interest of Columbia | 46.20% |  |
WPSC ownership interest of Columbia | 31.80% |  |

X
- Definition Rate MGE is entitled to a carrying cost on the related construction costs of the Columbia expenditures related to the construction of air emission reduction systems and associated equipment on Columbia Units 1 and 2. + References No definition available. + Details
Name: | mgee_CarryingCostOnPreConstructionCost
Namespace Prefix: | mgee_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Expected capital expenditures to be incurred during construction of an asset. + References No definition available. + Details
Name: | mgee_ExpectedCapitalExpenditures
Namespace Prefix: | mgee_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | mgee_ExpectedCapitalExpendituresLineItems
Namespace Prefix: | mgee_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition A jointly owned utility plant's share of MGE's net generating capability. + References No definition available. + Details
Name: | mgee_JointlyOwnedUtilityPlantFacilityShareOfMgeNetGeneratingCapability
Namespace Prefix: | mgee_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition WPL's proportionate share of interest (percent) in Columbia, a jointly owned utility plant. + References No definition available. + Details
Name: | mgee_JointlyOwnedUtilityPlantProportionateOwnershipShareWpl
Namespace Prefix: | mgee_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition WPSC's proportionate share of interest (percent) in Columbia, a jointly owned utility plant. + References No definition available. + Details
Name: | mgee_JointlyOwnedUtilityPlantProportionateOwnershipShareWpsc
Namespace Prefix: | mgee_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Rate MGE is entitled to earn a return on construction work in progress as approved in the current rate case for the year. + References No definition available. + Details
Name: | mgee_PublicUtilitiesPercentRateOfReturn
Namespace Prefix: | mgee_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Gross amount, at the balance sheet date, of long-lived assets under construction that include construction costs to date on capital projects that have not been completed and assets being constructed that are not ready to be placed into service. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 5 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 + Details
Name: | us-gaap_ConstructionInProgressGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_JointlyOwnedUtilityPlantInterestsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The proportionate share of interest (percent) in a jointly owned utility plant. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section C Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 10.C) -URI http://asc.fasb.org/extlink&oid=6500719&loc=d3e659983-123033 + Details
Name: | us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The component of the allowance for funds used during construction during the period based on an assumed rate of return on equity funds used in financing the construction of regulated assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 71 -Paragraph 15 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. 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 Reference 3: 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 + Details
Name: | us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration