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Employee Benefit Plans (Summary of Changes in Pension and Other Postretirement Benefit Plans) (Detail) - USD ($) | 1 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Dec. 31, 2019 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Jun. 30, 2019
Changes in fair value of plan assets: |  |  |  |  |  |
Employer contributions |  |  | $ 499,000,000 |  |  |
Amounts recognized in the Consolidated Balance Sheets at December 31: |  |  |  |  |  |
Noncurrent pension and other postretirement benefit assets |  | $ 1,708,000,000 | 1,708,000,000 | $ 1,279,000,000 |  |
Dominion Energy Gas Holdings, LLC |  |  |  |  |  |
Changes in fair value of plan assets: |  |  |  |  |  |
Employer contributions |  | 0 |  |  |  |
Amounts recognized in the Consolidated Balance Sheets at December 31: |  |  |  |  |  |
Noncurrent pension and other postretirement benefit assets | [1] | 840,000,000 | 840,000,000 | 705,000,000 |  |
Noncurrent Assets of Discontinued Operations |  |  |  | 5,849,000,000 |  |
Noncurrent liabilities of discontinued operations |  |  |  | (2,896,000,000) |  |
Pension Benefits |  |  |  |  |  |
Changes in benefit obligation: |  |  |  |  |  |
Benefit obligation at beginning of year |  |  | 8,500,000,000 | 9,052,000,000 |  |
Service cost |  |  | 162,000,000 | 157,000,000 | $ 138,000,000 |
Interest cost |  |  | 394,000,000 | 337,000,000 | 345,000,000 |
Benefits paid |  |  | (470,000,000) | (358,000,000) |  |
Actuarial (gains) losses during the year |  |  | 1,054,000,000 | (688,000,000) |  |
Settlements and curtailments | [2] |  | (48,000,000) |  |  |
Benefit obligation at end of year |  | 10,446,000,000 | 10,446,000,000 | 8,500,000,000 | 9,052,000,000 |
Changes in fair value of plan assets: |  |  |  |  |  |
Fair value of plan assets at beginning of year |  |  | 7,197,000,000 | 8,062,000,000 |  |
Dominion Energy SCANA Combination |  |  | 727,000,000 |  |  |
Actual return (loss) on plan assets |  |  | 1,747,000,000 | (513,000,000) |  |
Employer contributions |  | 520,000,000 | 557,000,000 | 6,000,000 |  |
Benefits paid |  |  | (470,000,000) | (358,000,000) |  |
Settlements |  |  | (127,000,000) |  |  |
Fair value of plan assets at end of year |  | 9,631,000,000 | 9,631,000,000 | 7,197,000,000 | 8,062,000,000 |
Funded status at end of year |  | (815,000,000) | (815,000,000) | (1,303,000,000) |  |
Amounts recognized in the Consolidated Balance Sheets at December 31: |  |  |  |  |  |
Noncurrent pension and other postretirement benefit assets |  | 1,266,000,000 | 1,266,000,000 | 1,003,000,000 |  |
Other current liabilities |  | (29,000,000) | (29,000,000) | (34,000,000) |  |
Noncurrent pension and other postretirement benefit liabilities |  | (2,052,000,000) | (2,052,000,000) | (2,272,000,000) |  |
Net amount recognized |  | $ (815,000,000) | $ (815,000,000) | $ (1,303,000,000) |  |
Significant assumptions used to determine benefit obligations as of December 31: |  |  |  |  |  |
Discount rate |  | 3.63% | 3.63% | 4.42% |  |
Weighted average rate of increase for compensation |  | 4.23% | 4.23% | 4.32% |  |
Pension Benefits | SCANA |  |  |  |  |  |
Changes in benefit obligation: |  |  |  |  |  |
Dominion Energy SCANA Combination |  |  | $ 854,000,000 |  |  |
Pension Benefits | Dominion Energy Gas Holdings, LLC |  |  |  |  |  |
Changes in benefit obligation: |  |  |  |  |  |
Benefit obligation at beginning of year |  |  | 730,000,000 | $ 773,000,000 |  |
Dominion Energy Gas Restructuring |  |  | (468,000,000) |  |  |
Service cost |  |  | 6,000,000 | 18,000,000 | 15,000,000 |
Interest cost |  |  | 11,000,000 | 29,000,000 | 30,000,000 |
Benefits paid |  |  | (15,000,000) | (34,000,000) |  |
Actuarial (gains) losses during the year |  |  | 30,000,000 | (56,000,000) |  |
Settlements and curtailments | [2] |  | 1,000,000 |  |  |
Benefit obligation at end of year |  | $ 295,000,000 | 295,000,000 | 730,000,000 | 773,000,000 |
Changes in fair value of plan assets: |  |  |  |  |  |
Fair value of plan assets at beginning of year |  |  | 1,656,000,000 | 1,803,000,000 |  |
Dominion Energy Gas Restructuring |  |  | (1,084,000,000) |  |  |
Actual return (loss) on plan assets |  |  | 129,000,000 | (113,000,000) |  |
Employer contributions |  |  | 0 |  |  |
Benefits paid |  |  | (15,000,000) | (34,000,000) |  |
Fair value of plan assets at end of year |  | 686,000,000 | 686,000,000 | 1,656,000,000 | 1,803,000,000 |
Funded status at end of year |  | 391,000,000 | 391,000,000 | 926,000,000 |  |
Amounts recognized in the Consolidated Balance Sheets at December 31: |  |  |  |  |  |
Noncurrent pension and other postretirement benefit assets |  | 391,000,000 | 391,000,000 | 310,000,000 |  |
Noncurrent Assets of Discontinued Operations |  |  |  | 616,000,000 |  |
Net amount recognized |  | $ 391,000,000 | $ 391,000,000 | $ 926,000,000 |  |
Significant assumptions used to determine benefit obligations as of December 31: |  |  |  |  |  |
Discount rate |  |  |  |  |  | 4.10%
Weighted average rate of increase for compensation |  | 4.64% | 4.64% | 4.55% |  |
Pension Benefits | Minimum |  |  |  |  |  |
Significant assumptions used to determine benefit obligations as of December 31: |  |  |  |  |  |
Discount rate |  | 3.47% | 3.47% | 4.42% |  | 4.07%
Pension Benefits | Maximum |  |  |  |  |  |
Significant assumptions used to determine benefit obligations as of December 31: |  |  |  |  |  |
Discount rate |  | 3.63% | 3.63% | 4.43% |  | 4.10%
Other Postretirement Benefits |  |  |  |  |  |
Changes in benefit obligation: |  |  |  |  |  |
Benefit obligation at beginning of year |  |  | $ 1,363,000,000 | $ 1,529,000,000 |  |
Service cost |  |  | 26,000,000 | 27,000,000 | 26,000,000 |
Interest cost |  |  | 68,000,000 | 56,000,000 | 60,000,000 |
Benefits paid |  |  | (96,000,000) | (87,000,000) |  |
Actuarial (gains) losses during the year |  |  | 111,000,000 | (158,000,000) |  |
Plan amendments |  |  |  | (4,000,000) |  |
Settlements and curtailments | [2] |  | 44,000,000 |  |  |
Benefit obligation at end of year |  | $ 1,769,000,000 | 1,769,000,000 | 1,363,000,000 | 1,529,000,000 |
Changes in fair value of plan assets: |  |  |  |  |  |
Fair value of plan assets at beginning of year |  |  | 1,581,000,000 | 1,729,000,000 |  |
Actual return (loss) on plan assets |  |  | 349,000,000 | (92,000,000) |  |
Employer contributions |  |  | 12,000,000 | 12,000,000 |  |
Benefits paid |  |  | (62,000,000) | (68,000,000) |  |
Fair value of plan assets at end of year |  | 1,880,000,000 | 1,880,000,000 | 1,581,000,000 | 1,729,000,000 |
Funded status at end of year |  | 111,000,000 | 111,000,000 | 218,000,000 |  |
Amounts recognized in the Consolidated Balance Sheets at December 31: |  |  |  |  |  |
Noncurrent pension and other postretirement benefit assets |  | 442,000,000 | 442,000,000 | 276,000,000 |  |
Other current liabilities |  | (17,000,000) | (17,000,000) | (2,000,000) |  |
Noncurrent pension and other postretirement benefit liabilities |  | (314,000,000) | (314,000,000) | (56,000,000) |  |
Net amount recognized |  | $ 111,000,000 | $ 111,000,000 | $ 218,000,000 |  |
Significant assumptions used to determine benefit obligations as of December 31: |  |  |  |  |  |
Discount rate |  | 3.44% | 3.44% | 4.37% |  |
Other Postretirement Benefits | SCANA |  |  |  |  |  |
Changes in benefit obligation: |  |  |  |  |  |
Dominion Energy SCANA Combination |  |  | $ 253,000,000 |  |  |
Other Postretirement Benefits | Dominion Energy Gas Holdings, LLC |  |  |  |  |  |
Changes in benefit obligation: |  |  |  |  |  |
Benefit obligation at beginning of year |  |  | 256,000,000 | $ 290,000,000 |  |
Dominion Energy Gas Restructuring |  |  | (135,000,000) |  |  |
Service cost |  |  | 1,000,000 | 4,000,000 | 4,000,000 |
Interest cost |  |  | 5,000,000 | 11,000,000 | 12,000,000 |
Benefits paid |  |  | (8,000,000) | (18,000,000) |  |
Actuarial (gains) losses during the year |  |  | 1,000,000 | (27,000,000) |  |
Plan amendments |  |  |  | (4,000,000) |  |
Settlements and curtailments | [2] |  | 1,000,000 |  |  |
Benefit obligation at end of year |  | $ 121,000,000 | 121,000,000 | 256,000,000 | 290,000,000 |
Changes in fair value of plan assets: |  |  |  |  |  |
Fair value of plan assets at beginning of year |  |  | 311,000,000 | 333,000,000 |  |
Dominion Energy Gas Restructuring |  |  | (126,000,000) |  |  |
Actual return (loss) on plan assets |  |  | 38,000,000 | (16,000,000) |  |
Employer contributions |  |  | 12,000,000 | 12,000,000 |  |
Benefits paid |  |  | (8,000,000) | (18,000,000) |  |
Fair value of plan assets at end of year |  | 227,000,000 | 227,000,000 | 311,000,000 | $ 333,000,000 |
Funded status at end of year |  | 106,000,000 | 106,000,000 | 55,000,000 |  |
Amounts recognized in the Consolidated Balance Sheets at December 31: |  |  |  |  |  |
Noncurrent pension and other postretirement benefit assets |  | 106,000,000 | 106,000,000 | 63,000,000 |  |
Noncurrent liabilities of discontinued operations |  |  |  | (8,000,000) |  |
Net amount recognized |  | $ 106,000,000 | $ 106,000,000 | $ 55,000,000 |  |
Significant assumptions used to determine benefit obligations as of December 31: |  |  |  |  |  |
Discount rate |  |  |  |  |  | 4.05%
Other Postretirement Benefits | Minimum |  |  |  |  |  |
Significant assumptions used to determine benefit obligations as of December 31: |  |  |  |  |  |
Discount rate |  | 3.44% | 3.44% | 4.37% |  | 4.05%
Other Postretirement Benefits | Maximum |  |  |  |  |  |
Significant assumptions used to determine benefit obligations as of December 31: |  |  |  |  |  |
Discount rate |  | 3.52% | 3.52% | 4.38% |  | 4.08%
[1] | See Note 25 for amounts attributable to related parties.
[2] | 2019 amounts relate primarily to a settlement as a result of the voluntary retirement program.

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