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Jointly Owned Electric Utility Plant - Ownership Interests in Jointly Owned Electric Plants and Transmission Facilities (Details) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 USD ($) V mi | Dec. 31, 2017 USD ($)
Pennsylvania [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Miles of transmission voltage lines | mi |  | 127 |
Transmission line capacity | V |  | 500 |
Delaware And New Jersey [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Miles of transmission voltage lines | mi |  | 151.3 |
Transmission line capacity | V |  | 500 |
Conemaugh [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Transmission line capacity | V |  | 500 |
Substation capacity | V |  | 500 |
Delaware River Crossing [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Miles of transmission voltage lines | mi |  | 2.5 |
Transmission line capacity | V |  | 500 |
New Freedom Switching [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Transmission line capacity | V |  | 500 |
Electric Transmission [Member] | Pennsylvania [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Plant | [1],[2] | $ 28 | $ 27
Accumulated depreciation | [1],[2] | 16 | 15
Construction work in progress | [2] | 1 | 0
Electric Transmission [Member] | Delaware And New Jersey [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Plant | [1],[3] | 103 | 102
Accumulated depreciation | [1],[3] | 53 | 52
Construction work in progress | [3] | 0 | 0
Other Service [Member] | Other Locations [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Plant | [1],[4] | 15 | 15
Accumulated depreciation | [1],[4] | 13 | 13
Construction work in progress | [4] | $ 0 | 0
Exelon Generation Co L L C [Member] | Merrill Creek [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 44.24% |
Exelon Generation Co L L C [Member] | Nuclear Plant [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 42.59% |
Exelon Generation Co L L C [Member] | Nuclear Plant [Member] | Quad Cities [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 75.00% |
Plant | [1] | $ 1,131 | 1,074
Accumulated depreciation | [1] | 587 | 550
Construction work in progress |  | $ 13 | 35
Exelon Generation Co L L C [Member] | Nuclear Plant [Member] | Peach Bottom [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 50.00% |
Plant | [1] | $ 1,451 | 1,417
Accumulated depreciation | [1] | 523 | 461
Construction work in progress |  | $ 15 | 18
Exelon Generation Co L L C [Member] | Nuclear Plant [Member] | Salem [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest | [5] | 42.59% |
Plant | [1],[5] | $ 648 | 631
Accumulated depreciation | [1],[5] | 227 | 205
Construction work in progress | [5] | $ 44 | 33
Exelon Generation Co L L C [Member] | Nuclear Plant [Member] | Nine Mile Point [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 82.00% |
Plant | [1] | $ 910 | 839
Accumulated depreciation | [1] | 126 | 97
Construction work in progress |  | 56 | 55
Exelon Generation Co L L C [Member] | Fossil Fuel Generation [Member] | Salem [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Plant |  | $ 3 |
Exelon Generation Co L L C [Member] | Fossil Fuel Generation [Member] | Wyman [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 5.89% |
Plant | [1] | $ 4 | 3
Accumulated depreciation | [1] | 3 | 3
Construction work in progress |  | $ 0 | $ 0
PECO Energy Co [Member] | Pennsylvania [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 22.00% |
PECO Energy Co [Member] | Delaware And New Jersey [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 42.55% |
PECO Energy Co [Member] | Conemaugh [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 20.72% |
PECO Energy Co [Member] | Delaware River Crossing [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 42.55% |
Baltimore Gas and Electric Company [Member] | Pennsylvania [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 7.00% |
Baltimore Gas and Electric Company [Member] | Conemaugh [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 10.56% |
Potomac Electric Power Company [Member] | Pennsylvania [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 27.00% |
Potomac Electric Power Company [Member] | Conemaugh [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 9.72% |
Potomac Electric Power Company [Member] | Valley Forge [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 11.90% |
Delmarva Power & Light Company [Member] | Pennsylvania [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 9.00% |
Delmarva Power & Light Company [Member] | Delaware And New Jersey [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 1.00% |
Delmarva Power & Light Company [Member] | Conemaugh [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 3.72% |
Delmarva Power & Light Company [Member] | Delaware River Crossing [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 7.45% |
Delmarva Power & Light Company [Member] | Merrill Creek [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 11.91% |
Delmarva Power & Light Company [Member] | Valley Forge [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 7.40% |
Atlantic City Electric Company [Member] | Pennsylvania [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 8.00% |
Atlantic City Electric Company [Member] | Delaware And New Jersey [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 13.90% |
Atlantic City Electric Company [Member] | Conemaugh [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 3.83% |
Atlantic City Electric Company [Member] | Delaware River Crossing [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 7.45% |
Atlantic City Electric Company [Member] | Merrill Creek [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 4.83% |
Atlantic City Electric Company [Member] | Valley Forge [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 6.60% |
Atlantic City Electric Company [Member] | New Freedom Switching [Member] |  |  |
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract] |  |  |
Ownership interest |  | 21.78% |
[1] | Excludes asset retirement costs and general plant.
[2] | PECO, BGE, Pepco, DPL and ACE own a 22%, 7%, 27%, 9% and 8% share, respectively, in 127 miles of 500kV lines located in Pennsylvania as well as a 20.72%, 10.56%, 9.72%, 3.72% and 3.83% share, respectively, of a 500kV substation immediately outside of the Conemaugh fossil-generating station which supplies power to the 500kV lines including, but not limited to, the lines noted above.
[3] | PECO, DPL and ACE own a 42.55%, 1% and 13.9% share, respectively in 151.3 miles of 500kV lines located in New Jersey and of the Salem generating plant substation. PECO, DPL and ACE also own a 42.55%, 7.45% and 7.45% share, respectively, in 2.5 miles of 500kV line located over the Delaware River. ACE also has a 21.78% share in a 500kV New Freedom Switching
[4] | Generation, DPL and ACE own a 44.24%, 11.91% and 4.83% share, respectively in assets located at Merrill Creek Reservoir located in New Jersey. Pepco, DPL and ACE own a 11.9%, 7.4% and 6.6% share, respectively, in Valley Forge Corporate Center.
[5] | Generation also owns a proportionate share in the fossil-fuel combustion turbine at Salem, which is fully depreciated. The gross book value was $3 million at December 31, 2018 and 2017.

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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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