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Joint Plant Ownership (Details) (USD $) | 12 Months Ended
--- | ---
Dec. 31, 2013 MW | Dec. 31, 2012 | Dec. 31, 2011
Columbia Units [Member] |  |  |
Jointly Owned Plants, Net Plant Ownership [Abstract] |  |  |
Plant | $ 123,097,000 | $ 119,544,000 |
Accumulated depreciation | (78,880,000) | (78,016,000) |
Property, plant, and equipment, net | 44,217,000 | 41,528,000 |
Construction work in progress | 120,858,000 | 59,917,000 |
Total property, plant, and equipment | 165,075,000 | 101,445,000 |
Columbia Units [Member] | MGE [Member] |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |
Jointly owned utility plant, proportion of total net summer generating capability | 31.00% |  |
Jointly owned utility plant, plant capacity (in MW) | 245 |  |
Jointly owned utility plant, ownership interest | 22.00% |  |
Jointly owned utility plant, fuel, operating, and maintenance expense | 37,500,000 | 36,300,000 | 37,100,000
Elm Road Units [Member] | MGE [Member] |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |
Jointly owned utility plant, fuel, operating, and maintenance expense | 13,400,000 | 13,200,000 | 18,000,000
Elm Road Units [Member] | MGE Power Elm Road [Member] |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |
Jointly owned utility plant, proportion of total net summer generating capability | 14.00% |  |
Jointly owned utility plant, plant capacity (in MW) | 106 |  |
Jointly owned utility plant, number of operating units | 2 |  |
Jointly Owned Plants, Net Plant Ownership [Abstract] |  |  |
Plant | 198,198,000 | 196,146,000 |
Accumulated depreciation | (15,541,000) | (11,126,000) |
Property, plant, and equipment, net | 182,657,000 | 185,020,000 |
Construction work in progress | 1,115,000 | 1,440,000 |
Total property, plant, and equipment | 183,772,000 | 186,460,000 |
Elm Road Unit 1 [Member] | MGE Power Elm Road [Member] |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |
Jointly owned utility plant, plant capacity (in MW) | 615 |  |
Jointly owned utility plant, ownership interest | 8.33% |  |
Elm Road Unit 2 [Member] | MGE Power Elm Road [Member] |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |
Jointly owned utility plant, plant capacity (in MW) | 615 |  |
Jointly owned utility plant, ownership interest | 8.33% |  |
West Campus [Member] | UW [Member] |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |
Jointly owned utility plant, ownership interest | 45.00% |  |
Jointly owned utility plant, fuel, operating, and maintenance expense | 4,900,000 | 4,900,000 | 5,000,000
West Campus [Member] | MGE Power West Campus [Member] |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |
Jointly owned utility plant, ownership interest | 55.00% |  |
Jointly Owned Plants, Net Plant Ownership [Abstract] |  |  |
Plant | 111,268,000 | 110,266,000 |
Accumulated depreciation | (21,704,000) | (19,927,000) |
Property, plant, and equipment, net | $ 89,564,000 | $ 90,339,000 |

X
- Definition Discloses entity portion of the fuel, operating, and maintenance expenses for the period. + References No definition available. + Details
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X
- Definition The total period end amount of plant in service net of accumulated depreciation for the utility's share of jointly owned electricity generation plant. + References No definition available. + Details
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- Definition The total operating capacity of each of the units in the jointly owned utility plant. + References No definition available. + Details
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- Definition A jointly owned utility plant's share of MGE's net generating capability. + References No definition available. + Details
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- Definition Number of operating units in the jointly owned utility plant. + References No definition available. + Details
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- Definition The period end amount owned by the reporting utility of a jointly owned utility plant in service. + References Reference 1: 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 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section C + Details
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- Definition The total period end amount of plant in service and construction in progress net of accumulated depreciation for the utility's share of jointly owned electricity generation plant. + References Reference 1: 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 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section C + Details
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- Definition The period end amount of construction work in progress at a jointly owned electricity generation plant. + References Reference 1: 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 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section C + Details
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- Definition The period end amount of accumulated depreciation in a jointly owned electricity generation plant. + References Reference 1: 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 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section C + Details
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- Definition The proportionate share of interest (percent) in a jointly owned utility plant. + References Reference 1: 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 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section C + Details
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