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Jointly Owned Plants (Details) $ in Millions | Dec. 31, 2017 USD ($)
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South Texas Project Units 1 and 2, Bay City, TX |
Jointly Owned Utility Plant Interests |
Ownership Interest (as a percent) | 44.00%
Property, Plant & Equipment | $ 395
Accumulated Depreciation | (207)
Construction in Progress | $ 7
Big Cajun II Unit 3, New Roads, LA |
Jointly Owned Utility Plant Interests |
Ownership Interest (as a percent) | 58.00%
Property, Plant & Equipment | $ 202
Accumulated Depreciation | (132)
Construction in Progress | $ 0
Cedar Bayou Unit 4, Baytown, TX |
Jointly Owned Utility Plant Interests |
Ownership Interest (as a percent) | 50.00%
Property, Plant & Equipment | $ 215
Accumulated Depreciation | (75)
Construction in Progress | $ 7
Keystone, Shelocta, PA |
Jointly Owned Utility Plant Interests |
Ownership Interest (as a percent) | 3.70%
Property, Plant & Equipment | $ 12
Accumulated Depreciation | 0
Construction in Progress | $ 1
Conemaugh, New Florence, PA |
Jointly Owned Utility Plant Interests |
Ownership Interest (as a percent) | 3.72%
Property, Plant & Equipment | $ 14
Accumulated Depreciation | 0
Construction in Progress | $ 1

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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 + 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 + 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 + 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 + Details
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