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Regulatory Matters Regulatory Matters - Schedule of Regulatory Asset Impairment (Details) $ in Millions | Dec. 31, 2017 USD ($)
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Amount of Impairment to Carrying Amount of Regulatory Assets | $ 35
Commonwealth Edison Co [Member] |
Amount of Impairment to Carrying Amount of Regulatory Assets | 3
Baltimore Gas and Electric Company [Member] |
Amount of Impairment to Carrying Amount of Regulatory Assets | 5
Pepco Holdings LLC [Member] |
Amount of Impairment to Carrying Amount of Regulatory Assets | 27
Potomac Electric Power Company [Member] |
Amount of Impairment to Carrying Amount of Regulatory Assets | 14
Delmarva Power & Light Company [Member] |
Amount of Impairment to Carrying Amount of Regulatory Assets | 6
Atlantic City Electric Company [Member] |
Amount of Impairment to Carrying Amount of Regulatory Assets | $ 7

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- Definition Discloses the amount of any reduction to the carrying amounts of regulated assets that result from impairment (for example, rate actions of a regulator). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 35 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6066304&loc=d3e44026-110379 + Details
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