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Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jan. 31, 2017 | Sep. 30, 2016 | Sep. 30, 2014 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Actual return (loss) on plan assets |  |  |  | $ 534 | $ (72) |
Expected return on pension and other postretirement plan assets |  |  |  | 691 | 648 |
Net actuarial loss |  |  |  |  | 25 |
Accumulated benefit obligation |  |  |  | 7,300 | 5,800 |
Estimated reduction in net cumulative required contributions |  |  |  | $ 200 |  |
Cumulative required contribution period (years) |  |  |  | 10 years |  |
Expected contribution to voluntary employees beneficiary association |  |  |  | $ 12 |  |
Amounts recognized in employer matching contributions |  |  |  | 44 | 43 | $ 41
Organizational Design Initiative | Special Termination Benefits |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Organizational design initiative charges |  |  |  | 65 |  |
Organizational design initiative charges, after tax |  |  |  | $ 40 |  |
Common and preferred stocks |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Defined benefit plan, actual plan asset allocation percentages |  |  |  | 28.00% |  |
Government securities |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Defined benefit plan, actual plan asset allocation percentages |  |  |  | 18.00% |  |
Fixed Income |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Defined benefit plan, actual plan asset allocation percentages |  |  |  | 35.00% |  |
Real estate funds |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Defined benefit plan, actual plan asset allocation percentages |  |  |  | 3.00% |  |
Other alternative investments |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Defined benefit plan, actual plan asset allocation percentages |  |  |  | 16.00% |  |
Capital Contribution to Dominion Questar to Fund Pension Contributions | Dominion Questar Corporation | Subsequent Event |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Capital contribution to Dominion Questar | $ 75 |  |  |  |  |
Collective Bargaining Agreement |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Period for experience study of employee demographics |  |  |  | 5 years |  |
Increase in net periodic benefit costs for 2017 |  |  |  | $ 42 |  |
Dominion Gas Holdings, LLC |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Actual return (loss) on plan assets |  |  |  | 130 | (13) |
Expected return on pension and other postretirement plan assets |  |  |  | 157 | 150 |
Net actuarial loss |  |  |  |  | 3 |
Accumulated benefit obligation |  |  |  | 640 | 578 |
Amounts recognized in employer matching contributions |  |  |  | 7 | 7 | 7
Dominion Gas Holdings, LLC | Organizational Design Initiative | Special Termination Benefits |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Organizational design initiative charges |  |  |  | 8 |  |
Organizational design initiative charges, after tax |  |  |  | 5 |  |
Dominion Gas Holdings, LLC | Dominion Retiree Health And Welfare Plan | Multiemployer Plans, Postretirement Benefit | Other operations and maintenance expense |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Net periodic benefit cost |  |  |  | (4) | (5) | (5)
Virginia Electric and Power Company |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Amounts recognized in employer matching contributions |  |  |  | 19 | 18 | 17
Virginia Electric and Power Company | Organizational Design Initiative | Special Termination Benefits |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Organizational design initiative charges |  |  |  | 33 |  |
Organizational design initiative charges, after tax |  |  |  | 20 |  |
Virginia Electric and Power Company | Other operations and maintenance expense |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Net periodic benefit cost |  |  |  | 79 | 97 | 75
Virginia Electric and Power Company | Dominion Retiree Health And Welfare Plan | Other operations and maintenance expense |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Net periodic benefit cost |  |  |  | (29) | (16) | (18)
Pension Benefits |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Actual return (loss) on plan assets |  |  |  | 426 | (71) |
Expected return on pension and other postretirement plan assets |  |  |  | 573 | 531 | $ 499
Net actuarial loss |  |  |  | (161) |  |
Actuarial (gains) losses during the year |  |  |  | $ 784 | $ (443) |
Discount rate (percentage) |  |  |  |  | 4.40% |
Expected long-term rate of return on plan assets (percentage) |  |  |  | 8.75% | 8.75% | 8.75%
Net periodic benefit cost |  |  |  | $ (25) | $ 44 | $ 20
Pension Benefits | Collective Bargaining Agreement |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Actuarial (gains) losses during the year |  |  |  | 290 |  |
Pension Benefits | Dominion Gas Holdings, LLC |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Actual return (loss) on plan assets |  |  |  | 107 | (14) |
Expected return on pension and other postretirement plan assets |  |  |  | 134 | 126 | $ 115
Net actuarial loss |  |  |  | (16) |  |
Actuarial (gains) losses during the year |  |  |  | $ 64 | $ (43) |
Discount percentage rate used for remeasurement |  |  |  | 4.50% | 4.99% |
Discount rate (percentage) |  |  |  | 4.99% | 4.40% | 5.20%
Expected long-term rate of return on plan assets (percentage) |  |  |  | 8.75% | 8.75% | 8.75%
Net periodic benefit cost |  |  |  | $ (78) | $ (63) | $ (55)
Pension Benefits | Dominion Gas Holdings, LLC | Other operations and maintenance expense |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Net periodic benefit cost |  |  |  | (45) | (38) | (37)
Pension Benefits | Dominion Gas Holdings, LLC | Collective Bargaining Agreement |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Actuarial (gains) losses during the year |  |  |  | 24 |  |
Other Postretirement Benefits |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Actual return (loss) on plan assets |  |  |  | 108 | (1) |
Expected return on pension and other postretirement plan assets |  |  |  | 118 | 117 | $ 111
Net actuarial loss |  |  |  | (13) |  |
Actuarial (gains) losses during the year |  |  |  | $ 166 | $ (138) |
Discount rate (percentage) |  |  |  |  | 4.40% |
Expected long-term rate of return on plan assets (percentage) |  |  |  | 8.50% | 8.50% | 8.50%
Net periodic benefit cost |  |  |  | $ (49) | $ (31) | $ (38)
Other Postretirement Benefits | Collective Bargaining Agreement |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Actuarial (gains) losses during the year |  |  |  | 38 |  |
Other Postretirement Benefits | Dominion Gas Holdings, LLC |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Actual return (loss) on plan assets |  |  |  | 23 | 1 |
Expected return on pension and other postretirement plan assets |  |  |  | 23 | 24 | $ 23
Net actuarial loss |  |  |  | (2) |  |
Actuarial (gains) losses during the year |  |  |  | $ 28 | $ (31) |
Discount percentage rate used for remeasurement |  |  |  | 4.47% | 4.93% |
Discount rate (percentage) |  |  |  | 4.93% | 4.40% |
Expected long-term rate of return on plan assets (percentage) |  |  |  | 8.50% | 8.50% | 8.50%
Net periodic benefit cost |  |  |  | $ (2) | $ (2) | $ (5)
Other Postretirement Benefits | Dominion Gas Holdings, LLC | Collective Bargaining Agreement |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Actuarial (gains) losses during the year |  |  |  | $ 9 |  |
Other Postretirement Benefits | East Ohio |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Retirement age |  |  | 65 years |  |  |
Increase (decrease) in accumulated postretirement benefit obligation due to amendment |  |  | $ 22 |  |  |
Increase (reduction) in net periodic benefit credit due to amendment (less than $1 million) |  |  | $ (1) |  |  |
Discount rate (percentage) |  |  | 4.20% |  |  |
Expected long-term rate of return on plan assets (percentage) |  |  | 8.50% |  |  |
Retiree medical coverage |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |  |  |
Retirement age |  | 65 years |  |  |  |
Increase (decrease) in accumulated postretirement benefit obligation due to amendment |  | $ (37) |  |  |  |
Increase (reduction) in net periodic benefit credit due to amendment (less than $1 million) |  | $ 9 |  |  |  |
Discount percentage rate used for remeasurement |  | 3.71% |  |  |  |

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- Definition Defined Benefit Plan, Assumptions Used in Calculations, Period of Employee Demographics used in Actuarial Study + References No definition available. + Details
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- Definition For defined benefit pension plans, the actuarial present value of benefits (whether vested or nonvested) attributed by the pension benefit formula to employee service rendered before a specified date and based on employee service and compensation (if applicable) before that date. The accumulated benefit obligation differs from the projected benefit obligation in that it includes no assumption about future compensation levels. For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Accumulated Benefit Obligation -URI http://asc.fasb.org/extlink&oid=6503844 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition The difference between fair value of plan assets at the end of the period and the fair value at the beginning of the period, adjusted for contributions and payments of benefits during the period, and after adjusting for taxes and other expenses, as applicable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Actual Return on Plan Assets (Component of Net Periodic Postretirement Benefit Cost) -URI http://asc.fasb.org/extlink&oid=6504192 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Actual Return on Plan Assets (Component of Net Periodic Pension Cost) -URI http://asc.fasb.org/extlink&oid=6504226 + Details
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- Definition Amount of gain (loss) related to change in benefit obligation resulting from changes in actuarial assumptions, for example, but not limited to, interest, mortality, employee turnover, salary, and temporary deviation from the substantive plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Gain or Loss -URI http://asc.fasb.org/extlink&oid=49168827 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition Amount included in accumulated other comprehensive income (AOCI) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position, including gain (loss), prior service cost (credit), and transition asset (obligation). + References No definition available. + Details
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- Definition The interest rate used to adjust for the time value of money for the plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Expected Long-Term Rate of Return on Plan Assets -URI http://asc.fasb.org/extlink&oid=6512046 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(3) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition The amount of increase or decrease in the accumulated benefit obligation related to the effects of a change in the substantive terms of an existing defined benefit pension plan or the initiation of a new plan. A plan amendment may increase or decrease benefits, including those attributed to years of service already rendered. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Plan Amendment -URI http://asc.fasb.org/extlink&oid=49173939 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (r) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition The amount of increase or decrease in net periodic benefit cost related to the effects of a change in the substantive terms of an existing defined benefit plan or the initiation of a new plan. A plan amendment may increase or decrease benefits, including those attributed to years of service already rendered. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Plan Amendment -URI http://asc.fasb.org/extlink&oid=49173939 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (r) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Prior Service Cost -URI http://asc.fasb.org/extlink&oid=49177896 + Details
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- Definition An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Expected Return on Plan Assets -URI http://asc.fasb.org/extlink&oid=6512171 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2446-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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