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Investments (Portion of Unrealized Gains and Losses Relates to Equity Securities) (Detail) $ in Millions | 12 Months Ended
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Dec. 31, 2018 USD ($)
Investment Holdings [Line Items] |  |
Net losses recognized during the period | $ (245) |
Less: Net gains recognized during the period on securities sold during the period | (58) |
Unrealized losses recognized during the period on securities still held at the end of the year | (303) | [1]
Virginia Electric and Power Company |  |
Investment Holdings [Line Items] |  |
Net losses recognized during the period | (105) |
Less: Net gains recognized during the period on securities sold during the period | (32) |
Unrealized losses recognized during the period on securities still held at the end of the year | $ (137) | [1]
[1] | Included in other income and the nuclear decommissioning trust regulatory liability as discussed in Note 2.

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- Definition Amount of realized gain from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=84241550&loc=SL75117546-209714 + Details
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- Definition Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=84241550&loc=SL75117546-209714 + Details
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- Definition Amount of unrealized loss on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=84241550&loc=SL75117546-209714 + Details
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