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EMPLOYEE RETIREMENT PLANS (Tables) | 9 Months Ended
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Dec. 31, 2017
Schedule of Carrying Value of Trust Assets and Obligations Under Supplemental Plan | The following table summarizes the carrying value of the trust assets and obligations under the supplemental plan:
|  | Successor |  |  | Predecessor |
(In thousands) |  | December 31, 2017 |  |  | March 31, 2017 |
Investments held in Rabbi Trust |  | $ | 8,908 |  |  |  | 8,759 |
Obligations under the supplemental plan |  |  | 32,508 |  |  |  | 29,108 |
Schedule of Unrealized (Loss) Gains in Carrying Value of Trust Assets | The following table summarizes the unrealized (loss) gains in carrying value of the trust assets:
|  | Successor |  |  | Predecessor |
(In thousands) |  | Period from August 1, 2017 through December 31, 2017 |  |  | Period from April 1, 2017 through July 31, 2017 |  |  | Year Ended March 31, 2017 |
Unrealized gain (loss) in carrying value of trust assets |  | $ | 256 |  |  |  | 82 |  |  |  | (95 | )
Unrealized loss in carrying value of trust assets are net of income tax expense of |  |  | — |  |  |  | — |  |  |  | (223 | )
Minimum and Maximum Rate of Return Plan Assets | The below table summarizes the supplemental plan’s minimum and maximum rate of return objectives for plan assets:
|  | Minimum Expected Rate of Return on Plan Assets |  |  | Maximum Expected Rate of Return on Plan Assets |
Equity securities |  |  | 5 | % |  |  | 7 | %
Debt securities |  |  | 1 | % |  |  | 3 | %
Cash and cash equivalents |  |  | 0 | % |  |  | 1 | %
Schedule of Minimum and Maximum Market Value of Plan Assets | The below table summarizes the supplemental plan’s minimum and maximum market value objectives for plan assets, which are based upon a five to ten year investment horizon:
|  | Minimum Market Value Objective for Plan Assets |  |  | Maximum Market Value Objective for Plan Assets |
Equity securities |  |  | 55 | % |  |  | 75 | %
Debt securities |  |  | 25 | % |  |  | 45 | %
Percentage of debt securities allowed in below investment grade bonds |  |  | 0 | % |  |  | 20 | %
Cash and cash equivalents |  |  | 0 | % |  |  | 10 | %
Schedule of Asset Allocations | The following table provides the target and actual asset allocations for the pension plan and the supplemental plan:
|  |  |  |  | Successor |  |  | Predecessor |
|  | Target |  |  | Actual as of December 31, 2017 |  |  | Actual as of March 31, 2017 |
U.S. Pension plan: |  |  |  |  |  |  |  |  |  |  |  |
Equity securities |  |  | — |  |  |  | — |  |  |  | — |
Debt securities |  |  | 100 | % |  |  | 98 | % |  |  | 98 | %
Cash and other |  |  | — |  |  |  | 2 | % |  |  | 2 | %
Total |  |  | 100 | % |  |  | 100 | % |  |  | 100 | %
Supplemental plan: |  |  |  |  |  |  |  |  |  |  |  |
Equity securities |  |  | 65 | % |  |  | 59 | % |  |  | 59 | %
Debt securities |  |  | 35 | % |  |  | 38 | % |  |  | 37 | %
Cash and other |  |  | — |  |  |  | 3 | % |  |  | 4 | %
Total |  |  | 100 | % |  |  | 100 | % |  |  | 100 | %
Fair Value Hierarchy of Plan Assets | The fair value hierarchy for the pension plans and supplemental plan assets measured at fair value as of December 31, 2017 (Successor), are as follows:
(In thousands) |  | Fair Value |  |  | Quoted prices in active markets (Level 1) |  |  | Significant observable inputs (Level 2) |  |  | Significant unobservable inputs (Level 3) |  |  | Measured at Net Asset Value |
Pension plan measured at fair value: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Government securities |  | $ | 4,238 |  |  |  | 4,238 |  |  |  | — |  |  |  | — |  |  |  | — |
Collateralized mortgage securities |  |  | 1,032 |  |  |  | — |  |  |  | 1,032 |  |  |  | — |  |  |  | — |
Corporate debt securities |  |  | 49,420 |  |  |  | — |  |  |  | 49,420 |  |  |  | — |  |  |  | — |
Cash and cash equivalents |  |  | 834 |  |  |  | 219 |  |  |  | 615 |  |  |  | — |  |  |  | — |
Other |  |  | 1,404 |  |  |  | 172 |  |  |  | 1,232 |  |  |  | — |  |  |  | — |
Total |  | $ | 56,928 |  |  |  | 4,629 |  |  |  | 52,299 |  |  |  | — |  |  |  | — |
Accrued income |  |  | 608 |  |  |  | 608 |  |  |  | — |  |  |  | — |  |  |  | — |
Total fair value of plan assets |  | $ | 57,536 |  |  |  | 5,237 |  |  |  | 52,299 |  |  |  | — |  |  |  | — |
Supplemental plan measured at fair value: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock |  | $ | 3,599 |  |  |  | 3,599 |  |  |  | — |  |  |  | — |  |  |  | — |
Foreign stock |  |  | 183 |  |  |  | 183 |  |  |  | — |  |  |  | — |  |  |  | — |
American depository receipts |  |  | 1,429 |  |  |  | 1,429 |  |  |  | — |  |  |  | — |  |  |  | — |
Preferred American depository receipts |  |  | 12 |  |  |  | 12 |  |  |  | — |  |  |  | — |  |  |  | — |
Real estate investment trusts |  |  | 72 |  |  |  | 72 |  |  |  | — |  |  |  | — |  |  |  | — |
Debt securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Government debt securities |  |  | 1,692 |  |  |  | 851 |  |  |  | 841 |  |  |  | — |  |  |  | — |
Open ended mutual funds |  |  | 1,676 |  |  |  | — |  |  |  | — |  |  |  | — |  |  |  | 1,676 |
Cash and cash equivalents |  |  | 246 |  |  |  | 27 |  |  |  | 170 |  |  |  | — |  |  |  | 49 |
Total |  | $ | 8,909 |  |  |  | 6,173 |  |  |  | 1,011 |  |  |  | — |  |  |  | 1,725 |
Other pending transactions |  |  | (1 | ) |  |  | (1 | ) |  |  | — |  |  |  | — |  |  |  | — |
Total fair value of plan assets |  | $ | 8,908 |  |  |  | 6,172 |  |  |  | 1,011 |  |  |  | — |  |  |  | 1,725 |
The following table provides the fair value hierarchy for the pension plans and supplemental plan assets measured at fair value as of March 31, 2017 (Predecessor):
(In thousands) |  | Fair Value |  |  | Quoted prices in active markets (Level 1) |  |  | Significant observable inputs (Level 2) |  |  | Significant unobservable inputs (Level 3) |  |  | Measured at Net Asset Value |
Pension plan measured at fair value: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Government securities |  | $ | 3,770 |  |  |  | 3,770 |  |  |  | — |  |  |  | — |  |  |  | — |
Collateralized mortgage securities |  |  | 2,537 |  |  |  | — |  |  |  | 2,537 |  |  |  | — |  |  |  | — |
Corporate debt securities |  |  | 47,871 |  |  |  | — |  |  |  | 47,871 |  |  |  | — |  |  |  | — |
Cash and cash equivalents |  |  | 989 |  |  |  | 345 |  |  |  | 644 |  |  |  | — |  |  |  | — |
Other |  |  | 1,298 |  |  |  | 100 |  |  |  | 1,198 |  |  |  | — |  |  |  | — |
Total |  | $ | 56,465 |  |  |  | 4,215 |  |  |  | 52,250 |  |  |  | — |  |  |  | — |
Accrued income |  |  | 681 |  |  |  | 681 |  |  |  | — |  |  |  | — |  |  |  | — |
Total fair value of plan assets |  | $ | 57,146 |  |  |  | 4,896 |  |  |  | 52,250 |  |  |  | — |  |  |  | — |
Supplemental plan measured at fair value: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock |  | $ | 3,561 |  |  |  | 3,561 |  |  |  | — |  |  |  | — |  |  |  | — |
Foreign stock |  |  | 132 |  |  |  | 132 |  |  |  | — |  |  |  | — |  |  |  | — |
American depository receipts |  |  | 1,387 |  |  |  | 1,387 |  |  |  | — |  |  |  | — |  |  |  | — |
Preferred American depository receipts |  |  | 20 |  |  |  | 20 |  |  |  | — |  |  |  | — |  |  |  | — |
Real estate investment trusts |  |  | 76 |  |  |  | 76 |  |  |  | — |  |  |  | — |  |  |  | — |
Debt securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Government debt securities |  |  | 1,613 |  |  |  | 832 |  |  |  | 781 |  |  |  | — |  |  |  | — |
Open ended mutual funds |  |  | 1,648 |  |  |  | — |  |  |  | — |  |  |  | — |  |  |  | 1,648 |
Cash and cash equivalents |  |  | 323 |  |  |  | 15 |  |  |  | 236 |  |  |  | — |  |  |  | 72 |
Total |  | $ | 8,760 |  |  |  | 6,023 |  |  |  | 1,017 |  |  |  | — |  |  |  | 1,720 |
Other pending transactions |  |  | — |  |  |  | — |  |  |  | — |  |  |  | — |  |  |  | — |
Total fair value of plan assets |  | $ | 8,760 |  |  |  | 6,023 |  |  |  | 1,017 |  |  |  | — |  |  |  | 1,720 |
Change in Plan Assets and Obligations | Changes in plan assets and obligations and the funded status of the U.S. defined benefit pension plan, Norway’s defined benefit pension plan, and the supplemental plan (referred to collectively as “Pension Benefits”) and the postretirement health care and life insurance plan (referred to as “Other Benefits”), are as follows:
|  | Pension Benefits |
|  | Successor |  |  | Predecessor |
(In thousands) |  | Period from August 1, 2017 through December 31, 2017 |  |  | Period from April 1, 2017 through July 31, 2017 |  |  | Year Ended March 31, 2017 |
Change in benefit obligation: |  |  |  |  |  |  |  |  |  |  |  |
Benefit obligation at beginning of the period |  | $ | 101,490 |  |  |  | 97,941 |  |  |  | 95,830 |
Service cost |  |  | 546 |  |  |  | 393 |  |  |  | 1,182 |
Interest cost |  |  | 1,599 |  |  |  | 1,313 |  |  |  | 3,814 |
Plan curtailment |  |  | (432 | ) |  |  | — |  |  |  |  |
Benefits paid |  |  | (2,059 | ) |  |  | (1,610 | ) |  |  | (4,895 | )
Actuarial (gain) loss |  |  | 2,322 |  |  |  | 3,322 |  |  |  | 2,082 |
Foreign currency exchange rate changes |  |  | (23 | ) |  |  | 131 |  |  |  | (72 | )
Benefit obligation at end of the period |  |  | 103,443 |  |  |  | 101,490 |  |  |  | 97,941 |
Change in plan assets: |  |  |  |  |  |  |  |  |  |  |  |
Fair value of plan assets at beginning of the period |  | $ | 58,148 |  |  |  | 57,146 |  |  |  | 57,174 |
Actual return |  |  | 1,182 |  |  |  | 2,138 |  |  |  | 577 |
Expected return |  |  | 32 |  |  |  | 16 |  |  |  | 51 |
Actuarial loss |  |  | (217 | ) |  |  | (109 | ) |  |  | (148 | )
Administrative expenses |  |  | (15 | ) |  |  | (7 | ) |  |  | (27 | )
Plan curtailment |  |  | (100 | ) |  |  | — |  |  |  | — |
Employer contributions |  |  | 625 |  |  |  | 435 |  |  |  | 4,465 |
Benefits paid |  |  | (2,059 | ) |  |  | (1,610 | ) |  |  | (4,895 | )
Foreign currency exchange rate changes |  |  | (60 | ) |  |  | 139 |  |  |  | (51 | )
Fair value of plan assets at end of the period |  |  | 57,536 |  |  |  | 58,148 |  |  |  | 57,146 |
Payroll tax unrecognized in benefit obligation at end of the period |  |  | 76 |  |  |  | 91 |  |  |  | 83 |
Unfunded status at end of the period |  | $ | (45,983 | ) |  |  | (43,433 | ) |  |  | (40,878 | )
Net amount recognized in the balance sheet consists of: |  |  |  |  |  |  |  |  |  |  |  |
Current liabilities |  | $ | (10,731 | ) |  |  | (1,791 | ) |  |  | (1,791 | )
Noncurrent liabilities |  |  | (35,252 | ) |  |  | (41,642 | ) |  |  | (39,087 | )
Net amount recognized |  | $ | (45,983 | ) |  |  | (43,433 | ) |  |  | (40,878 | )
|  | Other Benefits |
|  | Successor |  |  | Predecessor |
(In thousands) |  | Period from August 1, 2017 through December 31, 2017 |  |  | Period from April 1, 2017 through July 31, 2017 |  |  | Year Ended March 31, 2017 |
Change in benefit obligation: |  |  |  |  |  |  |  |  |  |  |  |
Benefit obligation at beginning of the period |  | $ | 4,817 |  |  |  | 4,811 |  |  |  | 5,573 |
Service cost |  |  | 29 |  |  |  | 23 |  |  |  | 81 |
Interest cost |  |  | 75 |  |  |  | 64 |  |  |  | 201 |
Participant contributions |  |  | 65 |  |  |  | 58 |  |  |  | 411 |
Plan amendment |  |  | (1,861 | ) |  |  | — |  |  |  | — |
Benefits paid |  |  | (526 | ) |  |  | (346 | ) |  |  | (1,170 | )
Actuarial (gain) loss |  |  | 325 |  |  |  | 207 |  |  |  | (285 | )
Benefit obligation at end of the period |  |  | 2,924 |  |  |  | 4,817 |  |  |  | 4,811 |
Change in plan assets: |  |  |  |  |  |  |  |  |  |  |  |
Fair value of plan assets at beginning of the period |  | $ | — |  |  |  | — |  |  |  | — |
Employer contributions |  |  | 461 |  |  |  | 288 |  |  |  | 759 |
Participant contributions |  |  | 65 |  |  |  | 58 |  |  |  | 411 |
Benefits paid |  |  | (526 | ) |  |  | (346 | ) |  |  | (1,170 | )
Fair value of plan assets at end of the period |  |  | — |  |  |  | — |  |  |  | — |
Unfunded status at end of the period |  | $ | (2,924 | ) |  |  | (4,817 | ) |  |  | (4,811 | )
Net amount recognized in the balance sheet consists of: |  |  |  |  |  |  |  |  |  |  |  |
Current liabilities |  | $ | (282 | ) |  |  | (418 | ) |  |  | (418 | )
Noncurrent liabilities |  |  | (2,642 | ) |  |  | (4,399 | ) |  |  | (4,393 | )
Net amount recognized |  | $ | (2,924 | ) |  |  | (4,817 | ) |  |  | (4,811 | )
Schedule of Projected and Accumulated Benefit Obligation | The following table provides the projected benefit obligation and accumulated benefit obligation for the pension plans:
|  | Successor |  |  | Predecessor |
(In thousands) |  | December 31, 2017 |  |  | March 31, 2017 |
Projected benefit obligation |  | $ | 103,443 |  |  |  | 97,941 |
Accumulated benefit obligation |  |  | 101,287 |  |  |  | 94,467 |
Schedule of Accumulated Benefit Obligation in Excess of Plan Assets | The following table provides information for pension plans with an accumulated benefit obligation in excess of plan assets (includes both the pension plans and supplemental plan):
|  | Successor |  |  | Predecessor |
(In thousands) |  | December 31, 2017 |  |  | March 31, 2017 |
Projected benefit obligation |  | $ | 103,443 |  |  |  | 97,941 |
Accumulated benefit obligation |  |  | 101,287 |  |  |  | 94,467 |
Fair value of plan assets |  |  | 57,536 |  |  |  | 57,146 |
Schedule of Net Periodic Benefit Cost | Net periodic benefit cost for the pension plans and the supplemental plan include the following components:
|  | Successor |  |  | Predecessor |
(In thousands) |  | Period from August 1, 2017 through December 31, 2017 |  |  | Period from April 1, 2017 through July 31, 2017 |  |  | Year Ended March 31, 2017 |
Service cost |  | $ | 546 |  |  |  | 393 |  |  |  | 1,182 |
Interest cost |  |  | 1,599 |  |  |  | 1,313 |  |  |  | 3,814 |
Expected return on plan assets |  |  | (882 | ) |  |  | (691 | ) |  |  | (2,246 | )
Administrational expenses |  |  | 19 |  |  |  | 3 |  |  |  | 28 |
Payroll tax of net pension costs |  |  | 29 |  |  |  | — |  |  |  | 56 |
Amortization of net actuarial losses |  |  | 131 |  |  |  | — |  |  |  | 32 |
Recognized actuarial loss |  |  | — |  |  |  | 748 |  |  |  | 1,785 |
Curtailment gain |  |  | (99 | ) |  |  | — |  |  |  | — |
Net periodic pension cost |  | $ | 1,343 |  |  |  | 1,766 |  |  |  | 4,651 |
Schedule of Net Periodic Benefit Cost for Postretirement Health Care and Life Insurance Plan | Net periodic benefit cost for the postretirement health care and life insurance plan include the following components:
|  | Successor |  |  | Predecessor |
(In thousands) |  | Period from August 1, 2017 through December 31, 2017 |  |  | Period from April 1, 2017 through July 31, 2017 |  |  | Year Ended March 31, 2017 |
Service cost |  | $ | 29 |  |  |  | 23 |  |  |  | 81 |
Interest cost |  |  | 75 |  |  |  | 64 |  |  |  | 201 |
Amortization of prior service cost |  |  | — |  |  |  | (927 | ) |  |  | (4,346 | )
Recognized actuarial (gain) |  |  | — |  |  |  | (335 | ) |  |  | (1,138 | )
Net periodic postretirement benefit |  | $ | 104 |  |  |  | (1,175 | ) |  |  | (5,202 | )
Schedule of Other Changes in Plan Assets and Benefit Obligations Recognized in OCI | Other changes in plan assets and benefit obligations recognized in other comprehensive (income) loss include the following components:
|  | Pension Benefits |
|  | Successor |  |  | Predecessor |
(In thousands) |  | Period from August 1, 2017 through December 31, 2017 |  |  | Period from April 1, 2017 through July 31, 2017 |  |  | Year Ended March 31, 2017 |
Net (gain) loss |  | $ | 1,939 |  |  |  | 1,877 |  |  |  | 3,821 |
Fresh-start accounting fair value adjustment |  |  | — |  |  |  | (22,333 | ) |  |  | — |
Amortization of net (loss) gain |  |  | — |  |  |  | (748 | ) |  |  | (1,785 | )
Total recognized in other comprehensive (income) loss, before tax |  | $ | 1,939 |  |  |  | (21,204 | ) |  |  | 2,036 |
Net of tax |  |  | 1,939 |  |  |  | (21,204 | ) |  |  | 1,323 |
|  | Other Benefits |
|  | Successor |  |  | Predecessor |
(In thousands) |  | Period from August 1, 2017 through December 31, 2017 |  |  | Period from April 1, 2017 through July 31, 2017 |  |  | Year Ended March 31, 2017 |
Net (gain) loss |  | $ | 325 |  |  |  | 207 |  |  |  | (285 | )
Prior service (cost) credit |  |  | (1,861 | ) |  |  | — |  |  |  | — |
Amortization of prior service (cost) credit |  |  | — |  |  |  | 927 |  |  |  | 4,346 |
Fresh-start accounting fair value adjustment |  |  | — |  |  |  | 19,055 |  |  |  | — |
Amortization of net (loss) gain |  |  | — |  |  |  | 335 |  |  |  | 1,138 |
Total recognized in other comprehensive (income) loss, before tax |  | $ | (1,536 | ) |  |  | 20,524 |  |  |  | 5,199 |
Net of tax |  |  | (1,536 | ) |  |  | 20,524 |  |  |  | 3,379 |
Schedule of Amounts Recognized in Accumulated Other Comprehensive Income (Loss) | Amounts recognized as a component of accumulated other comprehensive income (loss) are as follows:
|  | Pension Benefits |
(In thousands) |  | Period from August 1, 2017 through December 31, 2017 |  |  | Period from April 1, 2017 through July 31, 2017 |
Unrecognized actuarial (loss) gain |  | $ | (1,939 | ) |  |  | — |
Pre-tax amount included in accumulated other comprehensive (loss) income |  | $ | (1,939 | ) |  |  | — |
|  | Other Benefits |
(In thousands) |  | Period from August 1, 2017 through December 31, 2017 |  |  | Period from April 1, 2017 through July 31, 2017 |
Unrecognized actuarial (loss) gain |  | $ | (325 | ) |  |  | — |
Unrecognized prior service credit (cost) |  |  | 1,861 |  |  |  | — |
Pre-tax amount included in accumulated other comprehensive (loss) income |  | $ | 1,536 |  |  |  | — |
Schedule of Expected Amounts Net Periodic Benefit Costs | The company expects to recognize the following amounts as a component of net periodic benefit costs during the next fiscal year:
(In thousands) |  | Pension Benefits |  |  | Other Benefits |
Unrecognized actuarial (loss) gain |  | $ | — |  |  |  | 299 |
Unrecognized prior service credit (cost) |  |  | — |  |  |  | (5 | )
Schedule of Assumptions | Assumptions used to determine net benefit obligations are as follows:
|  | Pension Benefits |  |  | Other Benefits |
|  | Successor |  |  | Predecessor |  |  | Successor |  |  | Predecessor |
|  | December 31, 2017 |  |  | March 31, 2017 |  |  | December 31, 2017 |  |  | March 31, 2017 |
Discount rate |  |  | 3.80 | % |  |  | 4.25 | % |  |  | 3.80 | % |  |  | 4.25 | %
Rates of annual increase in compensation levels |  |  | N/A |  |  |  | 3.00 | % |  |  | N/A |  |  |  | N/A |
Assumptions used to determine net periodic benefit costs are as follows:
|  | Pension Benefits |  |  | Other Benefits |
|  | Successor |  |  | Predecessor |  |  | Successor |  |  | Predecessor |
|  | December 31, 2017 |  |  | March 31, 2017 |  |  | December 31, 2017 |  |  | March 31, 2017 |
Discount rate |  |  | 3.90 | % |  |  | 4.15 | % |  |  | 3.90 | % |  |  | 4.00 | %
Expected long-term rate of return on assets |  |  | 3.70 | % |  |  | 4.10 | % |  |  | N/A |  |  |  | N/A |
Rates of annual increase in compensation levels |  |  | 3.00 | % |  |  | 3.00 | % |  |  | N/A |  |  |  | N/A |
Schedule of Expected Benefit Payments | Based upon the assumptions used to measure the company’s qualified pension and postretirement benefit obligations at December 31, 2017, including pension and postretirement benefits attributable to estimated future employee service, the company expects that benefits to be paid over the next ten years will be as follows:
|  | (In thousands) |
Year ending December 31, |  | Pension Benefits |  |  | Other Benefits |
2018 |  | $ | 15,350 |  |  |  | 282 |
2019 |  |  | 5,812 |  |  |  | 301 |
2020 |  |  | 5,877 |  |  |  | 311 |
2021 |  |  | 5,966 |  |  |  | 302 |
2022 |  |  | 5,978 |  |  |  | 287 |
2023 – 2027 |  |  | 30,440 |  |  |  | 1,212 |
Total 10-year estimated future benefit payments |  | $ | 69,423 |  |  |  | 2,695 |
Assumed Health Care Cost Trends Rates | The following table discloses the assumed health care cost trends used in measuring the accumulated postretirement benefit obligation and net periodic postretirement benefit cost at December 31, 2017 for pre-65 medical and prescription drug coverage, including expected future trend rates.
|  | Pre-65 |
Year ending December 31, 2017: |  |  |  |
Accumulated postretirement benefit obligation |  |  | 7.60 | %
Net periodic postretirement benefit obligation |  |  | 7.60 | %
Ultimate health care cost trend |  |  | 4.54 | %
Ultimate year health care cost trend rate is achieved |  |  | 2038 |
Year ending December 31, 2018: |  |  |  |
Net periodic postretirement benefit obligation |  |  | 7.45 | %
One-Percentage Rate Change in Assumed Health Care Cost Trend Rates and Its Effects on Accumulated Postretirement Benefit Obligation | A one-percentage rate increase (decrease) in the assumed health care cost trend rates has the following effects on the accumulated postretirement benefit obligation as of December 31:
(In thousands) |  | 1% Increase |  |  | 1% Decrease |
Accumulated postretirement benefit obligation |  | $ | 10,715 |  |  |  | 9,603 |
Aggregate service and interest cost |  |  | 208,009 |  |  |  | 188,345 |
Number of Tidewater Common Stock Shares, Series A Warrants and Series B Warrants Held | The plan held the following number of shares of Tidewater common stock, series A warrants and series B warrants:
|  | Successor |  |  | Predecessor |
|  | Period from August 1, 2017 through December 31, 2017 |  |  | Period from April 1, 2017 through July 31, 2017 |  |  | Year Ended March 31, 2017 |
Number of shares of Tidewater common stock held by 401(k) plan |  |  | 8,074 |  |  |  | 264,504 |  |  |  | 291,957 |
Number of shares of Tidewater Series A warrants held by 401(k) plan |  |  | 9,030 |  |  |  | — |  |  |  | — |
Number of shares of Tidewater Series B warrants held by 401(k) plan |  |  | 9,762 |  |  |  | — |  |  |  | — |
Plan 401 k |
Amounts Charged to Expense Related to Contribution Plans | The amounts charged to expense related to the above defined contribution plans are as follows:
|  | Successor |  |  | Predecessor |
(In thousands) |  | Period from August 1, 2017 through December 31, 2017 |  |  | Period from April 1, 2017 through July 31, 2017 |  |  | Year Ended March 31, 2017 |
Defined contribution plans expense, net of forfeitures |  | $ | 854 |  |  |  | 871 |  |  |  | 2,660 |
Defined contribution plans forfeitures |  |  | 83 |  |  |  | 79 |  |  |  | 149 |
Multinational Retirement Plan |
Amounts Charged to Expense Related to Contribution Plans | The amounts charged to expense related to the multinational retirement plan and multinational savings plan contributions are as follows:
|  | Successor |  |  | Predecessor |
(In thousands) |  | Period from August 1, 2017 through December 31, 2017 |  |  | Period from April 1, 2017 through July 31, 2017 |  |  | Year Ended March 31, 2017 |
Multinational plan expense |  | $ | 81 |  |  |  | 67 |  |  |  | 260 |

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