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Commitments and Contingencies Commitments and Contingencies - Schedule of Minimum Future Operating Lease Payments (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Nov. 30, 2016
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Operating Leases Future Minimum Payments Due [Line Items] |  |  |  |
2018 | [1],[2] | $ 140 |  |
2019 | [1],[2] | 149 |  |
2020 | [1],[2] | 143 |  |
2021 | [1],[2] | 126 |  |
2022 | [1],[2] | 97 |  |
Remaining Years | [1],[2] | 723 |  |
Total minimum future lease payments | [1],[2] | 1,378 |  |
Exelon Generation Co L L C [Member] |  |  |  |
Operating Leases Future Minimum Payments Due [Line Items] |  |  |  |
2018 | [1],[2] | 33 |  |
2019 | [1],[2] | 46 |  |
2020 | [1],[2] | 46 |  |
2021 | [1],[2] | 47 |  |
2022 | [1],[2] | 46 |  |
Remaining Years | [1],[2] | 545 |  |
Total minimum future lease payments | [1],[2] | 763 |  |
Commonwealth Edison Co [Member] |  |  |  |
Operating Leases Future Minimum Payments Due [Line Items] |  |  |  |
2018 | [2],[3] | 7 |  |
2019 | [2],[3] | 5 |  |
2020 | [2],[3] | 4 |  |
2021 | [2],[3] | 4 |  |
2022 | [2],[3] | 3 |  |
Remaining Years | [2],[3] | 0 |  |
Total minimum future lease payments | [2],[3] | 23 |  |
Commonwealth Edison Co [Member] | Real Estate Leases and Railroad Licenses [Member] |  |  |  |
Operating Leases Future Minimum Payments Due [Line Items] |  |  |  |
Total minimum future lease payments |  | 3 |  |
PECO Energy Co [Member] |  |  |  |
Operating Leases Future Minimum Payments Due [Line Items] |  |  |  |
2018 | [2],[3] | 5 |  |
2019 | [2],[3] | 5 |  |
2020 | [2],[3] | 5 |  |
2021 | [2],[3] | 5 |  |
2022 | [2],[3] | 5 |  |
Remaining Years | [2],[3] | 0 |  |
Total minimum future lease payments | [2],[3] | 25 |  |
PECO Energy Co [Member] | Real Estate Leases and Railroad Licenses [Member] |  |  |  |
Operating Leases Future Minimum Payments Due [Line Items] |  |  |  |
Total minimum future lease payments |  | 5 |  |
Baltimore Gas and Electric Company [Member] |  |  |  |
Operating Leases Future Minimum Payments Due [Line Items] |  |  |  |
2018 |  | 35 | [2],[3],[4],[5] | $ 26
2019 |  | 35 | [2],[3],[4],[5] | 28
2020 |  | 33 | [2],[3],[4],[5] | 28
2021 |  | 18 | [2],[3],[4],[5] | $ 14
2022 | [2],[3],[4],[5] | 3 |  |
Remaining Years | [2],[3],[4],[5] | 19 |  |
Total minimum future lease payments | [2],[3],[4],[5] | 143 |  |
Baltimore Gas and Electric Company [Member] | Real Estate Leases and Railroad Licenses [Member] |  |  |  |
Operating Leases Future Minimum Payments Due [Line Items] |  |  |  |
Total minimum future lease payments |  | 1 |  |
Pepco Holdings LLC [Member] |  |  |  |
Operating Leases Future Minimum Payments Due [Line Items] |  |  |  |
2018 | [2] | 48 |  |
2019 | [2] | 46 |  |
2020 | [2] | 43 |  |
2021 | [2] | 42 |  |
2022 | [2] | 39 |  |
Remaining Years | [2] | 159 |  |
Total minimum future lease payments | [2] | 377 |  |
Potomac Electric Power Company [Member] |  |  |  |
Operating Leases Future Minimum Payments Due [Line Items] |  |  |  |
2018 | [2] | 11 |  |
2019 | [2] | 10 |  |
2020 | [2] | 9 |  |
2021 | [2] | 8 |  |
2022 | [2] | 8 |  |
Remaining Years | [2] | 40 |  |
Total minimum future lease payments | [2] | 86 |  |
Delmarva Power & Light Company [Member] |  |  |  |
Operating Leases Future Minimum Payments Due [Line Items] |  |  |  |
2018 | [2],[3] | 14 |  |
2019 | [2],[3] | 13 |  |
2020 | [2],[3] | 12 |  |
2021 | [2],[3] | 12 |  |
2022 | [2],[3] | 10 |  |
Remaining Years | [2],[3] | 35 |  |
Total minimum future lease payments | [2],[3] | 96 |  |
Delmarva Power & Light Company [Member] | Real Estate Leases and Railroad Licenses [Member] |  |  |  |
Operating Leases Future Minimum Payments Due [Line Items] |  |  |  |
Total minimum future lease payments |  | 1 |  |
Atlantic City Electric Company [Member] |  |  |  |
Operating Leases Future Minimum Payments Due [Line Items] |  |  |  |
2018 | [2] | 7 |  |
2019 | [2] | 6 |  |
2020 | [2] | 5 |  |
2021 | [2] | 5 |  |
2022 | [2] | 4 |  |
Remaining Years | [2] | 5 |  |
Total minimum future lease payments | [2] | $ 32 |  |
[1] | )Excludes Generation’s contingent operating lease payments associated with contracted generation agreement
[2] | )Includes amounts related to shared use land arrangement
[3] | )Amounts related to certain real estate leases and railroad licenses effectively have indefinite payment periods. As a result, ComEd, PECO, BGE and DPL have excluded these payments from the remaining years as such amounts would not be meaningful. ComEd's, PECO’s, BGE’s and DPL's average annual obligation for these arrangements, included in each of the years 2019 - 2023, was $3 million, $5 million, $1 million and $1 million respectivel
[4] | )The BGE column above includes minimum future lease payments associated with a 6-year lease for the Baltimore City conduit system that became effective during the fourth quarter of 2016. BGE's total commitments under the lease agreement are $26 million, $28 million, $28 million and $14 million related to years 2019 - 2022 , respectivel
[5] | )The BGE column above includes minimum future lease payments associated with a 6-year lease for the Baltimore City conduit system that became effective during the fourth quarter of 2016. BGE's total commitments under the lease agreement are $26 million, $28 million, $28 million and $14 million related to years 2019 - 2022 , respectivel

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- Definition Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697 + Details
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- Definition Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697 + Details
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- Definition Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717 + Details
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