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Employee Benefit Plans (Summary of Changes in Pension and Other Postretirement Benefit Plans) (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2016 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Changes in fair value of plan assets: |  |  |  |  |
Actual return (loss) on plan assets |  |  | $ 534 | $ (72) |
Dominion Gas Holdings, LLC |  |  |  |  |
Changes in fair value of plan assets: |  |  |  |  |
Actual return (loss) on plan assets |  |  | 130 | (13) |
Pension Benefits |  |  |  |  |
Changes in benefit obligation: |  |  |  |  |
Benefit obligation at beginning of year |  |  | 6,391 | 6,667 |
Dominion Questar Combination |  |  | 817 | 0 |
Service cost |  |  | 118 | 126 | $ 114
Interest cost |  |  | 317 | 287 | 290
Benefits paid |  |  | (286) | (246) |
Actuarial (gains) losses during the year |  |  | 784 | (443) |
Plan amendments | [1] |  | 0 | 0 |
Settlements and curtailments | [2] |  | (9) | 0 |
Benefit obligation at end of year |  |  | 8,132 | 6,391 | 6,667
Changes in fair value of plan assets: |  |  |  |  |
Fair value of plan assets at beginning of year |  |  | 6,166 | 6,480 |
Dominion Questar Combination |  |  | 704 | 0 |
Actual return (loss) on plan assets |  |  | 426 | (71) |
Employer contributions |  |  | 15 | 3 |
Benefits paid |  |  | (286) | (246) |
Settlements | [2] |  | (9) | 0 |
Fair value of plan assets at end of year |  |  | 7,016 | 6,166 | 6,480
Funded status at end of year |  |  | (1,116) | (225) |
Noncurrent pension and other postretirement benefit assets |  |  | 930 | 931 |
Other current liabilities |  |  | (43) | (14) |
Noncurrent pension and other postretirement benefit liabilities |  |  | (2,003) | (1,142) |
Net amount recognized |  |  | $ (1,116) | $ (225) |
Weighted average rate of increase for compensation (percentage) |  |  | 4.09% | 4.22% |
Pension Benefits | Minimum |  |  |  |  |
Changes in fair value of plan assets: |  |  |  |  |
Discount percentage rate |  |  | 3.31% | 4.96% |
Pension Benefits | Maximum |  |  |  |  |
Changes in fair value of plan assets: |  |  |  |  |
Discount percentage rate |  |  | 4.50% | 4.99% |
Pension Benefits | Dominion Gas Holdings, LLC |  |  |  |  |
Changes in benefit obligation: |  |  |  |  |
Benefit obligation at beginning of year |  |  | $ 608 | $ 638 |
Service cost |  |  | 13 | 15 | 12
Interest cost |  |  | 30 | 27 | 28
Benefits paid |  |  | (32) | (29) |
Actuarial (gains) losses during the year |  |  | 64 | (43) |
Benefit obligation at end of year |  |  | 683 | 608 | 638
Changes in fair value of plan assets: |  |  |  |  |
Fair value of plan assets at beginning of year |  |  | 1,467 | 1,510 |
Actual return (loss) on plan assets |  |  | 107 | (14) |
Employer contributions |  |  | 0 | 0 |
Benefits paid |  |  | (32) | (29) |
Fair value of plan assets at end of year |  |  | 1,542 | 1,467 | 1,510
Funded status at end of year |  |  | 859 | 859 |
Noncurrent pension and other postretirement benefit assets |  |  | 859 | 859 |
Noncurrent pension and other postretirement benefit liabilities | [3] |  | 0 | 0 |
Net amount recognized |  |  | $ 859 | $ 859 |
Discount percentage rate |  |  | 4.50% | 4.99% |
Weighted average rate of increase for compensation (percentage) |  |  | 4.11% | 3.93% |
Other Postretirement Benefits |  |  |  |  |
Changes in benefit obligation: |  |  |  |  |
Benefit obligation at beginning of year |  |  | $ 1,430 | $ 1,571 |
Dominion Questar Combination |  |  | 85 | 0 |
Service cost |  |  | 31 | 40 | 32
Interest cost |  |  | 65 | 67 | 67
Benefits paid |  |  | (83) | (79) |
Actuarial (gains) losses during the year |  |  | 166 | (138) |
Plan amendments | [1] |  | (216) | (31) |
Settlements and curtailments | [2] |  | 0 | 0 |
Benefit obligation at end of year |  |  | 1,478 | 1,430 | 1,571
Changes in fair value of plan assets: |  |  |  |  |
Fair value of plan assets at beginning of year |  |  | 1,382 | 1,402 |
Dominion Questar Combination |  |  | 45 | 0 |
Actual return (loss) on plan assets |  |  | 108 | (1) |
Employer contributions |  |  | 12 | 12 |
Benefits paid |  |  | (35) | (31) |
Settlements | [2] |  | 0 | 0 |
Fair value of plan assets at end of year |  |  | 1,512 | 1,382 | 1,402
Funded status at end of year |  |  | 34 | (48) |
Noncurrent pension and other postretirement benefit assets |  |  | 148 | 12 |
Other current liabilities |  |  | (5) | (3) |
Noncurrent pension and other postretirement benefit liabilities |  |  | (109) | (57) |
Net amount recognized |  |  | $ 34 | $ (48) |
Weighted average rate of increase for compensation (percentage) |  |  | 3.29% | 4.22% |
Other Postretirement Benefits | Minimum |  |  |  |  |
Changes in fair value of plan assets: |  |  |  |  |
Discount percentage rate |  |  | 3.92% | 4.93% |
Other Postretirement Benefits | Maximum |  |  |  |  |
Changes in fair value of plan assets: |  |  |  |  |
Discount percentage rate |  |  | 4.47% | 4.94% |
Other Postretirement Benefits | Dominion Gas Holdings, LLC |  |  |  |  |
Changes in benefit obligation: |  |  |  |  |
Benefit obligation at beginning of year |  |  | $ 292 | $ 320 |
Service cost |  |  | 5 | 7 | 6
Interest cost |  |  | 14 | 14 | 13
Benefits paid |  |  | (19) | (18) |
Actuarial (gains) losses during the year |  |  | 28 | (31) |
Benefit obligation at end of year |  |  | 320 | 292 | 320
Changes in fair value of plan assets: |  |  |  |  |
Fair value of plan assets at beginning of year |  |  | 283 | 288 |
Actual return (loss) on plan assets |  |  | 23 | 1 |
Employer contributions |  |  | 12 | 12 |
Benefits paid |  |  | (19) | (18) |
Fair value of plan assets at end of year |  |  | 299 | 283 | $ 288
Funded status at end of year |  |  | (21) | (9) |
Noncurrent pension and other postretirement benefit assets |  |  | 0 | 0 |
Noncurrent pension and other postretirement benefit liabilities | [3] |  | (21) | (9) |
Net amount recognized |  |  | $ (21) | $ (9) |
Discount percentage rate |  |  | 4.47% | 4.93% |
Weighted average rate of increase for compensation (percentage) |  |  |  | 3.93% |
Retiree medical coverage |  |  |  |  |
Changes in fair value of plan assets: |  |  |  |  |
Discount percentage rate |  | 3.71% |  |  |
Retirement age |  | 65 years |  |  |
[1] | 2016 amount relates primarily to a plan amendment that changed post-65 retiree medical coverage for certain current and future Local 50 retirees effective April 1, 2017. 2015 amount relates primarily to a plan amendment that changed retiree medical benefits for certain nonunion employees after Medicare eligibility.
[2] | Relates primarily to a settlement for certain executives.
[3] | Reflected in other deferred credits and other liabilities in Dominion Gas' Consolidated Balance Sheets.

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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 The aggregate net amount recognized in the balance sheet associated with the defined benefit plan(s). Will normally be the same as the Defined Benefit Plan, Funded Status of Plan, Total. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=21915240&loc=d3e1703-114919 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + 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 Expected rate of compensation increases (for pay-related plans). + 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)(2) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition 1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date. + 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 (a) -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 -Glossary Projected Benefit Obligation -URI http://asc.fasb.org/extlink&oid=6522206 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Accumulated Postretirement Benefit Obligation -URI http://asc.fasb.org/extlink&oid=6503904 + Details
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- Definition The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Benefits -URI http://asc.fasb.org/extlink&oid=49170737 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(6) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Postretirement Benefits -URI http://asc.fasb.org/extlink&oid=6521376 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(5) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 35 -Paragraph 50 -URI http://asc.fasb.org/extlink&oid=49178875&loc=d3e12355-114930 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) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition The funded status is measured as the difference between the fair value of plan assets and the benefit obligation. Will normally be the same as the net Defined Benefit Plan, Amounts Recognized in Balance Sheet, Total. + 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 (c) -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 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=21915240&loc=d3e1703-114919 + Details
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- Definition The amount that relates to an irrevocable action that relieves the employer (or the plan) of primary responsibility for a benefit obligation and eliminates significant risks related to the obligation and the assets used to effect the settlement. Examples of transactions that constitute a settlement include (a) making lump-sum cash payments to plan participants in exchange for their rights to receive specified benefits and (b) purchasing nonparticipating annuity contracts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 15 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=7577095&loc=d3e8001-114927 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)(8) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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