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Investments (Portion of Unrealized Gains and Losses Relates to Equity Securities) (Detail) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 | Jun. 30, 2018
Investment Holdings [Line Items] |  |  |
Net gains recognized during the period |  | $ 89 | $ 24
Less: Net gains recognized during the period on securities sold during the period |  | (16) | (35)
Unrealized gains (losses) recognized during the period on securities still held at June 30, 2018 | [1] | 73 | (11)
Virginia Electric and Power Company |  |  |
Investment Holdings [Line Items] |  |  |
Net gains recognized during the period |  | 44 | 12
Less: Net gains recognized during the period on securities sold during the period |  | (8) | (23)
Unrealized gains (losses) recognized during the period on securities still held at June 30, 2018 | [1] | $ 36 | $ (11)
[1] | Included in other income and the nuclear decommissioning trust regulatory liability as discussed in Note 2.

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- Definition Net gains and losses recognized on equity securities. + References No definition available. + Details
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- Definition The difference between the carrying value and the sale price of equity securities, not separately or otherwise categorized as trading or available-for-sale. This element includes investments in which the entity holds a small ownership stake (generally, less than 20% of the shares outstanding) and cannot exert significant influence. + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Amount of unrealized gain (loss) recognized in the income statement on unsold other securities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585 + Details
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- Details
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