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Employee Benefit Plans (Tables) | 12 Months Ended
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Dec. 31, 2016
General Discussion of Pension and Other Postretirement Benefits [Abstract] |
Pension plan and other postretirement benefit plan obligations and plan assets and includes a statement of the plans funded status | The following table summarizes the changes in pension plan and other postretirement benefit plan obligations and plan assets and includes a statement of the plans' funded status for Dominion and Dominion Gas (for employees represented by collective bargaining units):
| Pension Benefits |  | Other Postretirement Benefits |
Year Ended December 31, | 2016 |  | 2015 |  | 2016 |  | 2015 |
(millions, except percentages) |  |  |  |
Dominion |  |  |  |
Changes in benefit obligation: |  |  |  |
Benefit obligation at beginning of year | $ | 6,391 |  | $ | 6,667 |  | $ | 1,430 |  | $ | 1,571 |
Dominion Questar Combination | 817 |  | — |  | 85 |  | — |
Service cost | 118 |  | 126 |  | 31 |  | 40 |
Interest cost | 317 |  | 287 |  | 65 |  | 67 |
Benefits paid | (286 | ) | (246 | ) | (83 | ) | (79 | )
Actuarial (gains) losses during the year | 784 |  | (443 | ) | 166 |  | (138 | )
Plan amendments(1) | — |  | — |  | (216 | ) | (31 | )
Settlements and curtailments(2) | (9 | ) | — |  | — |  | — |
Benefit obligation at end of year | $ | 8,132 |  | $ | 6,391 |  | $ | 1,478 |  | $ | 1,430 |
Changes in fair value of plan assets: |  |  |  |  |  |  |  |
Fair value of plan assets at beginning of year | $ | 6,166 |  | $ | 6,480 |  | $ | 1,382 |  | $ | 1,402 |
Dominion Questar Combination | 704 |  | — |  | 45 |  | — |
Actual return (loss) on plan assets | 426 |  | (71 | ) | 108 |  | (1 | )
Employer contributions | 15 |  | 3 |  | 12 |  | 12 |
Benefits paid | (286 | ) | (246 | ) | (35 | ) | (31 | )
Settlements(2) | (9 | ) | — |  | — |  | — |
Fair value of plan assets at end of year | $ | 7,016 |  | $ | 6,166 |  | $ | 1,512 |  | $ | 1,382 |
Funded status at end of year | $ | (1,116 | ) | $ | (225 | ) | $ | 34 |  | $ | (48 | )
Amounts recognized in the Consolidated Balance Sheets at December 31: |  |  |  |  |  |  |  |
Noncurrent pension and other postretirement benefit assets | $ | 930 |  | $ | 931 |  | $ | 148 |  | $ | 12 |
Other current liabilities | (43 | ) | (14 | ) | (5 | ) | (3 | )
Noncurrent pension and other postretirement benefit liabilities | (2,003 | ) | (1,142 | ) | (109 | ) | (57 | )
Net amount recognized | $ | (1,116 | ) | $ | (225 | ) | $ | 34 |  | $ | (48 | )
Significant assumptions used to determine benefit obligations as of December 31: |  |  |  |  |  |  |  |
Discount rate | 3.31% - 4.50% |  | 4.96% - 4.99% |  | 3.92% - 4.47% |  | 4.93% - 4.94% |
Weighted average rate of increase for compensation | 4.09 | % | 4.22 | % | 3.29 | % | 4.22 | %
Dominion Gas |  |  |  |
Changes in benefit obligation: |  |  |  |
Benefit obligation at beginning of year | $ | 608 |  | $ | 638 |  | $ | 292 |  | $ | 320 |
Service cost | 13 |  | 15 |  | 5 |  | 7 |
Interest cost | 30 |  | 27 |  | 14 |  | 14 |
Benefits paid | (32 | ) | (29 | ) | (19 | ) | (18 | )
Actuarial (gains) losses during the year | 64 |  | (43 | ) | 28 |  | (31 | )
Benefit obligation at end of year | $ | 683 |  | $ | 608 |  | $ | 320 |  | $ | 292 |
Changes in fair value of plan assets: |  |  |  |  |  |  |  |
Fair value of plan assets at beginning of year | $ | 1,467 |  | $ | 1,510 |  | $ | 283 |  | $ | 288 |
Actual return (loss) on plan assets | 107 |  | (14 | ) | 23 |  | 1 |
Employer contributions | — |  | — |  | 12 |  | 12 |
Benefits paid | (32 | ) | (29 | ) | (19 | ) | (18 | )
Fair value of plan assets at end of year | $ | 1,542 |  | $ | 1,467 |  | $ | 299 |  | $ | 283 |
Funded status at end of year | $ | 859 |  | $ | 859 |  | $ | (21 | ) | $ | (9 | )
Amounts recognized in the Consolidated Balance Sheets at December 31: |  |  |  |  |  |  |  |
Noncurrent pension and other postretirement benefit assets | $ | 859 |  | $ | 859 |  | $ | — |  | $ | — |
Noncurrent pension and other postretirement benefit liabilities(3) | — |  | — |  | (21 | ) | (9 | )
Net amount recognized | $ | 859 |  | $ | 859 |  | $ | (21 | ) | $ | (9 | )
Significant assumptions used to determine benefit obligations as of December 31: |  |  |  |  |  |  |  |
Discount rate | 4.50 | % | 4.99 | % | 4.47 | % | 4.93 | %
Weighted average rate of increase for compensation | 4.11 | % | 3.93 | % | n/a |  | 3.93 | %
(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.
Benefit obligation in excess of plan asset | The following table provides information on the benefit obligations and fair value of plan assets for plans with a benefit obligation in excess of plan assets for Dominion and Dominion Gas (for employees represented by collective bargaining units):
| Pension Benefits | Other Postretirement Benefits
As of December 31, | 2016 |  | 2015 |  | 2016 |  | 2015 |
(millions) |  |  |  |
Dominion |  |  |  |
Benefit obligation | $ | 7,386 |  | $ | 5,728 |  | $ | 470 |  | $ | 359 |
Fair value of plan assets | 5,340 |  | 4,571 |  | 356 |  | 299 |
Dominion Gas |  |  |  |
Benefit obligation | $ | — |  | $ | — |  | $ | 320 |  | $ | 292 |
Fair value of plan assets | — |  | — |  | 299 |  | 283 |
Accumulated benefit obligation in excess of plan assets | The following table provides information on the ABO and fair value of plan assets for Dominion’s pension plans with an ABO in excess of plan assets:
As of December 31, | 2016 |  | 2015 |
(millions) |  |
Accumulated benefit obligation | $ | 5,987 |  | $ | 5,198 |
Fair value of plan assets | 4,653 |  | 4,571 |
Benefit payments expected future service | The following benefit payments, which reflect expected future service, as appropriate, are expected to be paid for Dominion’s and Dominion Gas’ (for employees represented by collective bargaining units) plans:
| Estimated Future Benefit Payments |
| Pension Benefits |  | Other Postretirement Benefits |
(millions) |  |
Dominion |  |
2017 | $ | 380 |  | $ | 92 |
2018 | 361 |  | 96 |
2019 | 373 |  | 97 |
2020 | 398 |  | 99 |
2021 | 415 |  | 100 |
2022-2026 | 2,345 |  | 490 |
Dominion Gas |  |
2017 | $ | 33 |  | $ | 17 |
2018 | 35 |  | 18 |
2019 | 37 |  | 19 |
2020 | 38 |  | 19 |
2021 | 40 |  | 20 |
2022-2026 | 211 |  | 101 |
Fair values of pension and post retirement plan assets by asset category | The fair values of Dominion's and Dominion Gas’ (for employees represented by collective bargaining units) pension plan assets by asset category are as follows:
At December 31, | 2016 | 2015
| Level 1 |  | Level 2 |  | Level 3 |  | Total |  | Level 1 |  | Level 2 |  | Level 3 |  | Total |
(millions) |  |  |  |  |  |  |  |
Dominion |  |  |  |  |  |  |  |
Cash and cash equivalents | $ | 12 |  | $ | 2 |  | $ | — |  | $ | 14 |  | $ | 16 |  | $ | — |  | $ | — |  | $ | 16 |
Common and preferred stocks: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. | 1,705 |  | — |  | — |  | 1,705 |  | 1,736 |  | — |  | — |  | 1,736 |
International | 928 |  | — |  | — |  | 928 |  | 786 |  | — |  | — |  | 786 |
Insurance contracts | — |  | 334 |  | — |  | 334 |  | — |  | 330 |  | — |  | 330 |
Corporate debt instruments | 35 |  | 682 |  | — |  | 717 |  | 44 |  | 695 |  | — |  | 739 |
Government securities | 13 |  | 522 |  | — |  | 535 |  | 85 |  | 390 |  | — |  | 475 |
Total recorded at fair value | $ | 2,693 |  | $ | 1,540 |  | $ | — |  | $ | 4,233 |  | $ | 2,667 |  | $ | 1,415 |  | $ | — |  | $ | 4,082 |
Assets recorded at NAV(1): |  |  |  |  |  |  |  |
Common/collective trust funds(2) |  |  |  | 1,960 |  |  |  |  | 1,200 |
Alternative investments: |  |  |  |  |  |  |  |
Real estate funds |  |  |  |  |  |  | 121 |  |  |  |  |  |  |  | 153 |
Private equity funds |  |  |  |  |  |  | 506 |  |  |  |  |  |  |  | 465 |
Debt funds |  |  |  |  |  |  | 153 |  |  |  |  |  |  |  | 170 |
Hedge funds |  |  |  |  |  |  | 25 |  |  |  |  |  |  |  | 86 |
Total recorded at NAV |  |  |  | $ | 2,765 |  |  |  |  | $ | 2,074 |
Total investments(3) |  |  |  |  |  |  | $ | 6,998 |  |  |  |  |  |  |  | $ | 6,156 |
Dominion Gas |  |  |  |  |  |  |  |
Cash and cash equivalents | $ | 3 |  | $ | — |  | $ | — |  | $ | 3 |  | $ | 4 |  | $ | — |  | $ | — |  | $ | 4 |
Common and preferred stocks: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. | 375 |  | — |  | — |  | 375 |  | 413 |  | — |  | — |  | 413 |
International | 203 |  | — |  | — |  | 203 |  | 187 |  | — |  | — |  | 187 |
Insurance contracts | — |  | 73 |  | — |  | 73 |  | — |  | 78 |  | — |  | 78 |
Corporate debt instruments | 8 |  | 150 |  | — |  | 158 |  | 10 |  | 165 |  | — |  | 175 |
Government securities | 3 |  | 115 |  | — |  | 118 |  | 20 |  | 93 |  | — |  | 113 |
Total recorded at fair value | $ | 592 |  | $ | 338 |  | $ | — |  | $ | 930 |  | $ | 634 |  | $ | 336 |  | $ | — |  | $ | 970 |
Assets recorded at NAV(1): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common/collective trust funds(4) |  |  |  |  |  |  | 430 |  |  |  |  |  |  |  | 286 |
Alternative investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Real estate funds |  |  |  |  |  |  | 27 |  |  |  |  |  |  |  | 36 |
Private equity funds |  |  |  |  |  |  | 111 |  |  |  |  |  |  |  | 111 |
Debt funds |  |  |  |  |  |  | 34 |  |  |  |  |  |  |  | 40 |
Hedge funds |  |  |  | 6 |  |  |  |  | 21 |
Total recorded at NAV |  |  |  |  |  |  | $ | 608 |  |  |  |  |  |  |  | $ | 494 |
Total investments(5) |  |  |  | $ | 1,538 |  |  |  |  | $ | 1,464 |
(1) These investments that are measured at fair value using the NAV per share (or its equivalent) as a practical expedient are not required to be categorized in the fair value hierarchy.
(2) | Also included in the common collective trust funds is the Northern Trust Collective Short-Term Investment Fund, totaling $167 million and $125 million at December 31, 2016 and 2015, respectively, which is comprised of money market instruments with short-term maturities used for temporary investment. Liquidity is emphasized to provide for redemption of units on any business day. Principal preservation is also a prime objective. Admissions and withdrawals are made daily. Interest is accrued daily and distributed monthly.
(3) | Includes net assets related to pending sales of securities of $46 million, net accrued income of $19 million, and excludes net assets related to pending purchases of securities of $47 million at December 31, 2016. Includes net assets related to pending sales of securities of $112 million, net accrued income of $16 million, and excludes net assets related to pending purchases of securities of $118 million at December 31, 2015.
(4) | Also included in the common collective trust funds is the Northern Trust Collective Short-Term Investment Fund, totaling $37 million and $30 million at December 31, 2016 and 2015, respectively, which is comprised of money market instruments with short-term maturities used for temporary investment. Liquidity is emphasized to provide for redemption of units on any business day. Principal preservation is also a prime objective. Admissions and withdrawals are made daily. Interest is accrued daily and distributed monthly.
(5) | Includes net assets related to pending sales of securities of $10 million, net accrued income of $4 million, and excludes net assets related to pending purchases of securities of $10 million at December 31, 2016. Includes net assets related to pending sales of securities of $27 million, net accrued income of $4 million, and excludes net assets related to pending purchases of securities of $28 million at December 31, 2015.
The fair values of Dominion's and Dominion Gas’ (for employees represented by collective bargaining units) other postretirement plan assets by asset category are as follows:
At December 31, | 2016 | 2015
| Level 1 |  | Level 2 |  | Level 3 |  | Total |  | Level 1 |  | Level 2 |  | Level 3 |  | Total |
(millions) |  |  |  |  |  |  |  |
Dominion |  |  |  |  |  |  |  |
Cash and cash equivalents | $ | 1 |  | $ | 1 |  | $ | — |  | $ | 2 |  | $ | 1 |  | $ | 1 |  | $ | — |  | $ | 2 |
Common and preferred stocks: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. | 571 |  | — |  | — |  | 571 |  | 531 |  | — |  | — |  | 531 |
International | 143 |  | — |  | — |  | 143 |  | 134 |  | — |  | — |  | 134 |
Insurance contracts | — |  | 19 |  | — |  | 19 |  | — |  | 18 |  | — |  | 18 |
Corporate debt instruments | 2 |  | 40 |  | — |  | 42 |  | 3 |  | 38 |  | — |  | 41 |
Government securities | 1 |  | 30 |  | — |  | 31 |  | 4 |  | 22 |  | — |  | 26 |
Total recorded at fair value | $ | 718 |  | $ | 90 |  | $ | — |  | $ | 808 |  | $ | 673 |  | $ | 79 |  | $ | — |  | $ | 752 |
Assets recorded at NAV(1): |  |  |  |  |  |  |  |
Common/collective trust funds(2) |  |  |  |  |  |  | 621 |  |  |  |  |  |  |  | 543 |
Alternative investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Real estate funds |  |  |  |  |  |  | 9 |  |  |  |  |  |  |  | 14 |
Private equity funds |  |  |  |  |  |  | 59 |  |  |  |  |  |  |  | 54 |
Debt funds |  |  |  |  |  |  | 12 |  |  |  |  |  |  |  | 14 |
Hedge funds |  |  |  |  |  |  | 1 |  |  |  |  |  |  |  | 5 |
Total recorded at NAV |  |  |  | $ | 702 |  |  |  |  | $ | 630 |
Total investments(3) |  |  |  |  |  |  | $ | 1,510 |  |  |  |  |  |  |  | $ | 1,382 |
Dominion Gas |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common and preferred stocks: |  |  |  |  |  |  |  |
U.S. | $ | 121 |  | $ | — |  | $ | — |  | $ | 121 |  | $ | 113 |  | $ | — |  | $ | — |  | $ | 113 |
International | 24 |  | — |  | — |  | 24 |  | 24 |  | — |  | — |  | 24 |
Total recorded at fair value | $ | 145 |  | $ | — |  | $ | — |  | $ | 145 |  | $ | 137 |  | $ | — |  | $ | — |  | $ | 137 |
Assets recorded at NAV(1): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common/collective trust funds(4) |  |  |  | 140 |  |  |  |  | 132 |
Alternative investments: |  |  |  |  |  |  |  |  |  |
Real estate funds |  |  |  | 1 |  |  |  |  | 2 |
Private equity funds |  |  |  |  |  |  | 12 |  |  |  |  |  |  |  | 11 |
Debt funds |  |  |  |  |  |  | 1 |  |  |  |  |  |  |  | 1 |
Total recorded at NAV |  |  |  | $ | 154 |  |  |  |  | $ | 146 |
Total investments |  |  |  | $ | 299 |  |  |  |  | $ | 283 |
(1) These investments that are measured at fair value using the NAV per share (or its equivalent) as a practical expedient are not required to be categorized in the fair value hierarchy.
(2) | Also included in the common collective trust funds is the Northern Trust Collective Short-Term Investment Fund, totaling $16 million and $9 million at December 31, 2016 and 2015, respectively, which is comprised of money market instruments with short-term maturities used for temporary investment. Liquidity is emphasized to provide for redemption of units on any business day. Principal preservation is also a prime objective. Admissions and withdrawals are made daily. Interest is accrued daily and distributed monthly.
(3) | Includes net assets related to pending sales of securities of $5 million, net accrued income of $2 million, and excludes net assets related to pending purchases of securities of $5 million at December 31, 2016.
(4) | Also included in the common collective trust funds is the Northern Trust Collective Short-Term Investment Fund, totaling $2 million and $3 million at December 31, 2016 and 2015, respectively, which is comprised of money market instruments with short-term maturities used for temporary investment. Liquidity is emphasized to provide for redemption of units on any business day. Principal preservation is also a prime objective. Admissions and withdrawals are made daily. Interest is accrued daily and distributed monthly.
Net periodic benefit (credit) cost and amounts recognized in other comprehensive income and regulatory assets and liabilities | The components of the provision for net periodic benefit (credit) cost and amounts recognized in other comprehensive income and regulatory assets and liabilities for Dominion’s and Dominion Gas’ (for employees represented by collective bargaining units) plans are as follows:
| Pension Benefits | Other Postretirement Benefits
Year Ended December 31, | 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014 |
(millions, except percentages) |  |  |  |  |  |
Dominion |  |  |  |  |  |
Service cost | $ | 118 |  | $ | 126 |  | $ | 114 |  | $ | 31 |  | $ | 40 |  | $ | 32 |
Interest cost | 317 |  | 287 |  | 290 |  | 65 |  | 67 |  | 67 |
Expected return on plan assets | (573 | ) | (531 | ) | (499 | ) | (118 | ) | (117 | ) | (111 | )
Amortization of prior service (credit) cost | 1 |  | 2 |  | 3 |  | (35 | ) | (27 | ) | (28 | )
Amortization of net actuarial loss | 111 |  | 160 |  | 111 |  | 8 |  | 6 |  | 2 |
Settlements and curtailments | 1 |  | — |  | 1 |  | — |  | — |  | — |
Net periodic benefit (credit) cost | $ | (25 | ) | $ | 44 |  | $ | 20 |  | $ | (49 | ) | $ | (31 | ) | $ | (38 | )
Changes in plan assets and benefit obligations recognized in other comprehensive income and regulatory assets and liabilities: |  |  |  |  |  |  |  |  |  |  |  |
Current year net actuarial (gain) loss | $ | 931 |  | $ | 159 |  | $ | 784 |  | $ | 178 |  | $ | (18 | ) | $ | 183 |
Prior service (credit) cost | — |  | — |  | — |  | (216 | ) | (31 | ) | 9 |
Settlements and curtailments | (1 | ) | — |  | (1 | ) | — |  | — |  | — |
Less amounts included in net periodic benefit cost: |  |  |  |  |  |  |  |  |  |  |  |
Amortization of net actuarial loss | (111 | ) | (160 | ) | (111 | ) | (8 | ) | (6 | ) | (2 | )
Amortization of prior service credit (cost) | (1 | ) | (2 | ) | (3 | ) | 35 |  | 27 |  | 28 |
Total recognized in other comprehensive income and regulatory assets and liabilities | $ | 818 |  | $ | (3 | ) | $ | 669 |  | $ | (11 | ) | $ | (28 | ) | $ | 218 |
Significant assumptions used to determine periodic cost: |  |  |  |  |  |  |  |  |  |  |  |
Discount rate | 2.87% - 4.99% |  | 4.40 | % | 5.20% - 5.30% |  | 3.56% - 4.94% |  | 4.40 | % | 4.20% - 5.10% |
Expected long-term rate of return on plan assets | 8.75 | % | 8.75 | % | 8.75 | % | 8.50 | % | 8.50 | % | 8.50 | %
Weighted average rate of increase for compensation | 4.22 | % | 4.22 | % | 4.21 | % | 4.22 | % | 4.22 | % | 4.22 | %
Healthcare cost trend rate(1) |  |  |  |  |  |  | 7.00 | % | 7.00 | % | 7.00 | %
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)(1) |  |  |  |  |  |  | 5.00 | % | 5.00 | % | 5.00 | %
Year that the rate reaches the ultimate trend rate(1)(2) |  |  |  | 2020 |  | 2019 |  | 2018 |
Dominion Gas |  |  |  |  |  |
Service cost | $ | 13 |  | $ | 15 |  | $ | 12 |  | $ | 5 |  | $ | 7 |  | $ | 6 |
Interest cost | 30 |  | 27 |  | 28 |  | 14 |  | 14 |  | 13 |
Expected return on plan assets | (134 | ) | (126 | ) | (115 | ) | (23 | ) | (24 | ) | (23 | )
Amortization of prior service (credit) cost | — |  | 1 |  | 1 |  | 1 |  | (1 | ) | (1 | )
Amortization of net actuarial loss | 13 |  | 20 |  | 19 |  | 1 |  | 2 |  | — |
Net periodic benefit (credit) cost | $ | (78 | ) | $ | (63 | ) | $ | (55 | ) | $ | (2 | ) | $ | (2 | ) | $ | (5 | )
Changes in plan assets and benefit obligations recognized in other comprehensive income and regulatory assets and liabilities: |  |  |  |  |  |  |  |  |  |  |  |
Current year net actuarial (gain) loss | $ | 91 |  | $ | 97 |  | $ | 43 |  | $ | 28 |  | $ | (9 | ) | $ | 40 |
Prior service cost | — |  | — |  | — |  | — |  | — |  | 10 |
Less amounts included in net periodic benefit cost: |  |  |  |  |  |  |  |  |  |  |  |
Amortization of net actuarial loss | (13 | ) | (20 | ) | (19 | ) | (1 | ) | (2 | ) | — |
Amortization of prior service credit (cost) | — |  | (1 | ) | (1 | ) | (1 | ) | 1 |  | 1 |
Total recognized in other comprehensive income and regulatory assets and liabilities | $ | 78 |  | $ | 76 |  | $ | 23 |  | $ | 26 |  | $ | (10 | ) | $ | 51 |
Significant assumptions used to determine periodic cost: |  |  |  |  |  |  |  |  |  |  |  |
Discount rate | 4.99 | % | 4.40 | % | 5.20 | % | 4.93 | % | 4.40 | % | 4.20% - 5.00% |
Expected long-term rate of return on plan assets | 8.75 | % | 8.75 | % | 8.75 | % | 8.50 | % | 8.50 | % | 8.50 | %
Weighted average rate of increase for compensation | 3.93 | % | 3.93 | % | 3.93 | % | 3.93 | % | 3.93 | % | 3.93 | %
Healthcare cost trend rate(1) |  |  |  |  |  |  | 7.00 | % | 7.00 | % | 7.00 | %
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)(1) |  |  |  |  |  |  | 5.00 | % | 5.00 | % | 5.00 | %
Year that the rate reaches the ultimate trend rate(1)(2) |  |  |  | 2020 |  | 2019 |  | 2018 |
(1) | Assumptions used to determine net periodic cost for the following year.
(2) | The Society of Actuaries model used to determine healthcare cost trend rates was updated in 2014. The new model converges to the ultimate trend rate much more quickly than previous models.
Components of AOCI and regulatory assets and liabilities that have not been recognized as components of periodic benefit (credit) cost | The components of AOCI and regulatory assets and liabilities for Dominion’s and Dominion Gas’ (for employees represented by collective bargaining units) plans that have not been recognized as components of net periodic benefit (credit) cost are as follows:
| Pension Benefits | Other Postretirement Benefits
At December 31, | 2016 |  | 2015 |  | 2016 |  | 2015 |
(millions) |  |  |  |
Dominion |  |  |  |
Net actuarial loss | $ | 3,200 |  | $ | 2,381 |  | $ | 283 |  | $ | 114 |
Prior service (credit) cost | 4 |  | 5 |  | (419 | ) | (237 | )
Total(1) | $ | 3,204 |  | $ | 2,386 |  | $ | (136 | ) | $ | (123 | )
Dominion Gas |  |  |  |
Net actuarial loss | $ | 458 |  | $ | 380 |  | $ | 60 |  | $ | 33 |
Prior service (credit) cost | — |  | 1 |  | 7 |  | 7 |
Total(2) | $ | 458 |  | $ | 381 |  | $ | 67 |  | $ | 40 |
(1) | As of December 31, 2016, of the $3.2 billion and $(136) million related to pension benefits and other postretirement benefits, $1.9 billion and $(103) million, respectively, are included in AOCI, with the remainder included in regulatory assets and liabilities. As of December 31, 2015, of the $2.4 billion and $(123) million related to pension benefits and other postretirement benefits, $1.4 billion and $(90) million, respectively, are included in AOCI, with the remainder included in regulatory assets and liabilities.
(2) | As of December 31, 2016, of the $458 million related to pension benefits, $167 million is included in AOCI, with the remainder included in regulatory assets and liabilities; the $67 million related to other postretirement benefits is included entirely in regulatory assets and liabilities. As of December 31, 2015, of the $381 million related to pension benefits, $138 million is included in AOCI, with the remainder included in regulatory assets and liabilities; the $40 million related to other postretirement benefits is included entirely in regulatory assets and liabilities.
Components of AOCI and regulatory assets and liabilities that are expected to be amortized as components of periodic benefit cost in 2017 | The following table provides the components of AOCI and regulatory assets and liabilities for Dominion’s and Dominion Gas’ (for employees represented by collective bargaining units) plans as of December 31, 2016 that are expected to be amortized as components of net periodic benefit (credit) cost in 2017:
| Pension Benefits |  | Other Postretirement Benefits |
(millions) |  |
Dominion |  |
Net actuarial loss | $ | 161 |  | $ | 13 |
Prior service (credit) cost | 1 |  | (47 | )
Dominion Gas |  |
Net actuarial loss | $ | 16 |  | $ | 2 |
Prior service (credit) cost | — |  | 1 |
Effect of one percentage point change on benefit plans | A one percentage point change in assumed healthcare cost trend rates would have had the following effects for Dominion’s and Dominion Gas’ (for employees represented by collective bargaining units) other postretirement benefit plans:
| Other Postretirement Benefits |
| One percentage point increase |  | One percentage point decrease |
(millions) |  |
Dominion |  |
Effect on net periodic cost for 2017 | $ | 23 |  | $ | (18 | )
Effect on other postretirement benefit obligation at December 31, 2016 | 152 |  | (127 | )
Dominion Gas |  |
Effect on net periodic cost for 2017 | $ | 5 |  | $ | (4 | )
Effect on other postretirement benefit obligation at December 31, 2016 | 41 |  | (34 | )

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