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Equity (Narrative) (Detail) $ in Millions |  | 1 Months Ended | 3 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | ---
Aug. 15, 2016 shares | [1] | Jan. 31, 2019 USD ($) shares | Dec. 31, 2018 USD ($) shares | Jun. 30, 2018 USD ($) shares | May 31, 2018 | Apr. 30, 2018 shares | Feb. 28, 2018 USD ($) Agreement | Jan. 31, 2018 USD ($) Performance_Factor shares | Jul. 31, 2017 USD ($) shares | Jun. 30, 2017 USD ($) Agreement | Jul. 31, 2016 shares | Apr. 30, 2016 USD ($) shares | Dec. 31, 2018 USD ($) shares | Dec. 31, 2019 shares | Dec. 31, 2018 USD ($) Performance_Factor shares | Dec. 31, 2017 USD ($) shares | Dec. 31, 2016 USD ($) shares | Sep. 30, 2015 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance of common stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 2,461 | $ 1,302 | $ 2,152 |
Common stock, shares outstanding | shares |  |  | 681,000,000 |  |  |  |  |  |  |  |  |  | 681,000,000 |  | 681,000,000 | 645,000,000 |  |
Issuance of common stock (in shares) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 2,461 | $ 1,302 | 2,152 |
Shares of common stock issued in acquisition | shares |  | 22,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Shares of common stock issued in acquisition, value |  | $ 1,600 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net proceeds from issuance of Dominion Midstream common units |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 4 | 18 | 482 |
Net proceeds from issuance of Dominion Midstream convertible preferred units |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 490 |
Conversion basis |  |  | 0.01 |  |  |  |  |  |  |  |  |  | 0.01 |  | 0.01 |  |  |
Subordinated unit conversion |  |  |  |  | 0.01 |  |  |  |  |  |  |  |  |  |  |  |  |
Number of shares received | shares |  |  |  | 26,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) Non-controlling interest |  |  |  | $ 375 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Compensation cost related to stock-based compensation |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 48 | 45 | 33 |
Tax benefit from stock awards and stock options exercised |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 12 | 16 | 11 |
Vesting period |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 years |  |  |
Cash Based Performance Grant | Officer |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash-based performance grants minimum percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.00% |  |  |
Cash-based performance grants maximum percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 200.00% |  |  |
February 2016 Cash Based Performance Grant | Officer |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of performance metrics achieved | Performance_Factor |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |  |  |
Expected award under grant |  |  |  |  |  |  |  | $ 12 |  |  |  |  |  |  |  |  |  |
February 2017 Cash Based Performance Grant [Member] | Officer |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of performance metrics achieved | Performance_Factor |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |
February 2017 Cash Based Performance Grant [Member] | Officer | Two-year grant |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Targeted amount of the grant |  |  | $ 13 |  |  |  |  |  |  |  |  |  | $ 13 |  | $ 13 |  |  |
Liability accrued for award |  |  | 13 |  |  |  |  |  |  |  |  |  | 13 |  | 13 |  |  |
February 2017 Cash Based Performance Grant [Member] | Officer | Three-year grant |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Targeted amount of the grant |  |  | 14 |  |  |  |  |  |  |  |  |  | 14 |  | 14 |  |  |
Liability accrued for award |  |  | 10 |  |  |  |  |  |  |  |  |  | 10 |  | $ 10 |  |  |
February 2018 Cash Based Performance Grant [Member] | Officer |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of performance metrics achieved | Performance_Factor |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |
February 2018 Cash Based Performance Grant [Member] | Officer | Three-year grant |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Targeted amount of the grant |  |  | 16 |  |  |  |  |  |  |  |  |  | 16 |  | $ 16 |  |  |
Liability accrued for award |  |  | $ 5 |  |  |  |  |  |  |  |  |  | $ 5 |  | $ 5 |  |  |
Dominion Direct Employee Stock Awards Employee Savings Plans Director Stock Compensation Plans and Contingent Convertible Senior Notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of shares for future agreement | shares |  |  | 76,000,000 |  |  |  |  |  |  |  |  |  | 76,000,000 |  | 76,000,000 |  |  |
Stock Based Awards |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Shares were available for future grants | shares |  |  | 22,000,000 |  |  |  |  |  |  |  |  |  | 22,000,000 |  | 22,000,000 |  |  |
Restricted Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unrecognized compensation cost related to nonvested awards |  |  | $ 49 |  |  |  |  |  |  |  |  |  | $ 49 |  | $ 49 |  |  |
Fair value of restricted stock awards that vested |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 23 | $ 21 | $ 21 |
Virginia Electric and Power Company |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance of common stock (in shares) | shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0 |
Common stock, shares outstanding | shares |  |  | 274,723 |  |  |  |  |  |  |  |  |  | 274,723 |  | 274,723 | 274,723 |  |
Repurchase of common stock, shares | shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  |
Virginia Electric and Power Company | Scenario, Forecast |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repurchase of common stock, shares | shares |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 |  |  |  |
Dominion Midstream Partners, LP | Limited Partner |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net proceeds from issuance of Dominion Midstream common units |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 18 | $ 482 |
Dominion Midstream Partners, LP | Limited Partner | Convertible Preferred Units |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net proceeds from issuance of Dominion Midstream convertible preferred units |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 490 |
Dominion Midstream Partners, LP | Dominion Midstream Limited Partner Common Unit Purchase Program | Limited Partner |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Authorized purchase amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 50
Stock repurchase program expiration date |  |  |  |  |  |  |  |  |  |  |  |  |  |  | Sep. 30, 2016 |  |  |
Number of common units purchased | shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 658,000 |
Value of common units purchased |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 17 |
Maximum | Stock Based Awards |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum term of stock based awards |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8 years |  |  |
Weighted Average | Restricted Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Expected weighted-average period recognized for the unrecognized compensation cost |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 years 1 month 6 days |  |  |
Noncontrolling Interests |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) Non-controlling interest |  |  |  | $ (375) |  |  |  |  |  |  |  |  |  |  |  |  |  |
Goldman Sachs & Co. and Credit Suisse LLC. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance of common stock |  |  | $ 1,400 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance of common stock (in shares) | shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 22,100,000 |  |  |
Number of shares for future agreement | shares |  |  |  |  |  | 20,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Capital Unit, Class A |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance of common stock |  |  |  |  |  |  |  |  | $ 1,000 |  |  |  |  |  |  |  |  |
Issuance of common stock (in shares) | shares | 28,000,000 |  |  |  |  |  |  |  | 12,500,000 |  |  |  |  |  |  |  |  |
Capital Unit, Class A | Remarketable Subordinated Notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance of common stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 1,100 |  |  |
Issuance of common stock (in shares) | shares |  |  |  |  |  |  |  |  | 12,500,000 |  | 8,500,000 | 8,500,000 |  |  |  |  |  |
Underwritten Public Offering |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance of common stock |  |  |  |  |  |  |  |  |  |  |  | $ 756 |  |  |  |  |  |
Issuance of common stock (in shares) | shares |  |  |  |  |  |  |  |  |  |  |  | 10,200,000 |  |  |  |  |  |
Various Programs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance of common stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 2,500 |  |  |
Issuance of common stock (in shares) | shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 36,000,000 |  |  |
Common stock, shares outstanding | shares |  |  | 681,000,000 |  |  |  |  |  |  |  |  |  | 681,000,000 |  | 681,000,000 |  |  |
Employee Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash proceeds received from issuance of shares through Dominion Direct and employee savings plans |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 315 |  |  |
Number of shares issued through Dominion Direct and employee savings plans | shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4,500,000 |  |  |
Shelf Registration for Sale of Common Stock through At-the-market Program |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance of common stock |  |  |  |  |  |  |  | $ 495 |  |  |  |  | $ 197 |  |  |  |  |
Issuance of common stock (in shares) | shares |  |  |  |  |  |  |  | 6,600,000 |  |  |  |  | 2,700,000 |  |  |  |  |
Number of sales agency agreements | Agreement |  |  |  |  |  |  | 6 |  |  | 3 |  |  |  |  |  |  |  |
Issuance of common stock (in shares) |  |  |  |  |  |  |  |  |  | $ 0 |  |  |  |  |  |  |  |
Fees and commissions paid |  |  |  |  |  |  |  | $ 5 |  |  |  |  | $ 2 |  |  |  |  |
Remaining ability to issue stock under the sales agency agreements |  |  | $ 801 |  |  |  |  |  |  |  |  |  | $ 801 |  | $ 801 |  |  |
Shelf Registration for Sale of Common Stock through At-the-market Program | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sale of stock authorized amount |  |  |  |  |  |  | $ 1,000 |  |  | $ 500 |  |  |  |  |  |  |  |
Underwriting Agreement | Goldman Sachs & Co. and Credit Suisse LLC. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Option exercised | shares |  |  |  |  |  | 2,100,000 |  |  |  |  |  |  |  |  |  |  |  |
[1] | The maturity dates of the $700 million Series A-1 RSNs and $700 million Series A-2 RSNs are August 15, 2021 and August 15, 2024, respectively.

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