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Change in Plan Assets and Obligations (Detail) - USD ($) $ in Thousands | 3 Months Ended | 4 Months Ended | 5 Months Ended | 6 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jul. 31, 2017 | Dec. 31, 2017 | Jun. 30, 2018 | Jun. 30, 2017 | Dec. 31, 2017 | Mar. 31, 2017 | Mar. 31, 2016
Schedule Of Pension And Other Postretirement Benefits Changes In Benefit Obligation And Fair Value Of Plan Assets [Line Items] |  |  |  |  |  |  |  |  |
Benefit obligation at beginning of the period |  |  |  |  | $ 103,443 |  |  |  |
Benefit obligation at end of the period |  |  |  | $ 103,443 |  |  | $ 103,443 |  |
Predecessor |  |  |  |  |  |  |  |  |
Schedule Of Pension And Other Postretirement Benefits Changes In Benefit Obligation And Fair Value Of Plan Assets [Line Items] |  |  |  |  |  |  |  |  |
Benefit obligation at beginning of the period |  | $ 97,941 | $ 97,941 |  |  |  | 97,941 |  |
Benefit obligation at end of the period |  |  |  |  |  |  |  | $ 97,941 |
Pension Plans, Defined Benefit |  |  |  |  |  |  |  |  |
Schedule Of Pension And Other Postretirement Benefits Changes In Benefit Obligation And Fair Value Of Plan Assets [Line Items] |  |  |  |  |  |  |  |  |
Employer contributions | $ 0 | 0 |  |  | 0 | $ 0 | 0 | 3,000 | $ 0
Current liabilities |  |  |  | (10,731) |  |  | (10,731) |  |
Noncurrent liabilities |  |  |  | (35,252) |  |  | (35,252) |  |
Net amount recognized |  |  |  | (45,983) |  |  | (45,983) |  |
Pension Plans, Defined Benefit | Predecessor |  |  |  |  |  |  |  |  |
Schedule Of Pension And Other Postretirement Benefits Changes In Benefit Obligation And Fair Value Of Plan Assets [Line Items] |  |  |  |  |  |  |  |  |
Actuarial (gain) loss |  |  | 748 |  |  |  |  | 1,785 |
Current liabilities |  |  | (1,791) |  |  |  |  | (1,791) |
Noncurrent liabilities |  |  | (41,642) |  |  |  |  | (39,087) |
Net amount recognized |  |  | (43,433) |  |  |  |  | (40,878) |
Pension Plans, Defined Benefit | Change in Benefit Obligations |  |  |  |  |  |  |  |  |
Schedule Of Pension And Other Postretirement Benefits Changes In Benefit Obligation And Fair Value Of Plan Assets [Line Items] |  |  |  |  |  |  |  |  |
Benefit obligation at beginning of the period |  |  |  | 101,490 | 103,443 |  |  |  |
Service cost |  |  |  | 546 |  |  |  |  |
Interest cost |  |  |  | 1,599 |  |  |  |  |
Plan curtailment |  |  |  | (432) |  |  |  |  |
Benefits paid |  |  |  | (2,059) |  |  |  |  |
Actuarial (gain) loss |  |  |  | 2,322 |  |  |  |  |
Foreign currency exchange rate changes |  |  |  | (23) |  |  |  |  |
Benefit obligation at end of the period |  |  | 101,490 | 103,443 |  |  | 103,443 |  |
Pension Plans, Defined Benefit | Change in Benefit Obligations | Predecessor |  |  |  |  |  |  |  |  |
Schedule Of Pension And Other Postretirement Benefits Changes In Benefit Obligation And Fair Value Of Plan Assets [Line Items] |  |  |  |  |  |  |  |  |
Benefit obligation at beginning of the period |  | 97,941 | 97,941 | 101,490 |  |  | 97,941 | 95,830 |
Service cost |  |  | 393 |  |  |  |  | 1,182 |
Interest cost |  |  | 1,313 |  |  |  |  | 3,814 |
Benefits paid |  |  | (1,610) |  |  |  |  | (4,895) |
Actuarial (gain) loss |  |  | 3,322 |  |  |  |  | 2,082 |
Foreign currency exchange rate changes |  |  | 131 |  |  |  |  | (72) |
Benefit obligation at end of the period |  |  | 101,490 |  |  |  |  | 97,941 | 95,830
Pension Plans, Defined Benefit | Change In Plan Assets |  |  |  |  |  |  |  |  |
Schedule Of Pension And Other Postretirement Benefits Changes In Benefit Obligation And Fair Value Of Plan Assets [Line Items] |  |  |  |  |  |  |  |  |
Fair value of plan assets at beginning of the period |  |  |  | 58,148 | 57,536 |  |  |  |
Actual return |  |  |  | 1,182 |  |  |  |  |
Expected return |  |  |  | 32 |  |  |  |  |
Actuarial (gain) loss |  |  |  | 217 |  |  |  |  |
Administrative expenses |  |  |  | (15) |  |  |  |  |
Plan curtailment |  |  |  | (100) |  |  |  |  |
Employer contributions |  |  |  | 625 |  |  |  |  |
Benefits paid |  |  |  | (2,059) |  |  |  |  |
Foreign currency exchange rate changes |  |  |  | (60) |  |  |  |  |
Fair value of plan assets at end of the period |  |  | 58,148 | 57,536 |  |  | 57,536 |  |
Payroll tax unrecognized in benefit obligation at end of the period |  |  |  | 76 |  |  | 76 |  |
Unfunded status at end of the period |  |  |  | (45,983) |  |  | (45,983) |  |
Pension Plans, Defined Benefit | Change In Plan Assets | Predecessor |  |  |  |  |  |  |  |  |
Schedule Of Pension And Other Postretirement Benefits Changes In Benefit Obligation And Fair Value Of Plan Assets [Line Items] |  |  |  |  |  |  |  |  |
Fair value of plan assets at beginning of the period |  | 57,146 | 57,146 | 58,148 |  |  | 57,146 | 57,174 |
Actual return |  |  | 2,138 |  |  |  |  | 577 |
Expected return |  |  | 16 |  |  |  |  | 51 |
Actuarial (gain) loss |  |  | 109 |  |  |  |  | 148 |
Administrative expenses |  |  | (7) |  |  |  |  | (27) |
Employer contributions |  |  | 435 |  |  |  |  | 4,465 |
Benefits paid |  |  | (1,610) |  |  |  |  | (4,895) |
Foreign currency exchange rate changes |  |  | 139 |  |  |  |  | (51) |
Fair value of plan assets at end of the period |  |  | 58,148 |  |  |  |  | 57,146 | 57,174
Payroll tax unrecognized in benefit obligation at end of the period |  |  | 91 |  |  |  |  | 83 |
Unfunded status at end of the period |  |  | (43,433) |  |  |  |  | (40,878) |
Other Pension Plans, Defined Benefit |  |  |  |  |  |  |  |  |
Schedule Of Pension And Other Postretirement Benefits Changes In Benefit Obligation And Fair Value Of Plan Assets [Line Items] |  |  |  |  |  |  |  |  |
Current liabilities |  |  |  | (282) |  |  | (282) |  |
Noncurrent liabilities |  |  |  | (2,642) |  |  | (2,642) |  |
Net amount recognized |  |  |  | (2,924) |  |  | (2,924) |  |
Other Pension Plans, Defined Benefit | Predecessor |  |  |  |  |  |  |  |  |
Schedule Of Pension And Other Postretirement Benefits Changes In Benefit Obligation And Fair Value Of Plan Assets [Line Items] |  |  |  |  |  |  |  |  |
Actuarial (gain) loss |  |  | (335) |  |  |  |  | (1,138) |
Current liabilities |  |  | (418) |  |  |  |  | (418) |
Noncurrent liabilities |  |  | (4,399) |  |  |  |  | (4,393) |
Net amount recognized |  |  | (4,817) |  |  |  |  | (4,811) |
Other Pension Plans, Defined Benefit | Change in Benefit Obligations |  |  |  |  |  |  |  |  |
Schedule Of Pension And Other Postretirement Benefits Changes In Benefit Obligation And Fair Value Of Plan Assets [Line Items] |  |  |  |  |  |  |  |  |
Benefit obligation at beginning of the period |  |  |  | 4,817 | $ 2,924 |  |  |  |
Service cost |  |  |  | 29 |  |  |  |  |
Interest cost |  |  |  | 75 |  |  |  |  |
Participant contributions |  |  |  | 65 |  |  |  |  |
Plan amendment |  |  |  | (1,861) |  |  |  |  |
Benefits paid |  |  |  | (526) |  |  |  |  |
Actuarial (gain) loss |  |  |  | 325 |  |  |  |  |
Benefit obligation at end of the period |  |  | 4,817 | 2,924 |  |  | 2,924 |  |
Other Pension Plans, Defined Benefit | Change in Benefit Obligations | Predecessor |  |  |  |  |  |  |  |  |
Schedule Of Pension And Other Postretirement Benefits Changes In Benefit Obligation And Fair Value Of Plan Assets [Line Items] |  |  |  |  |  |  |  |  |
Benefit obligation at beginning of the period |  | $ 4,811 | 4,811 | 4,817 |  |  | 4,811 | 5,573 |
Service cost |  |  | 23 |  |  |  |  | 81 |
Interest cost |  |  | 64 |  |  |  |  | 201 |
Participant contributions |  |  | 58 |  |  |  |  | 411 |
Benefits paid |  |  | (346) |  |  |  |  | (1,170) |
Actuarial (gain) loss |  |  | 207 |  |  |  |  | (285) |
Benefit obligation at end of the period |  |  | 4,817 |  |  |  |  | 4,811 | $ 5,573
Other Pension Plans, Defined Benefit | Change In Plan Assets |  |  |  |  |  |  |  |  |
Schedule Of Pension And Other Postretirement Benefits Changes In Benefit Obligation And Fair Value Of Plan Assets [Line Items] |  |  |  |  |  |  |  |  |
Employer contributions |  |  |  | 461 |  |  |  |  |
Participant contributions |  |  |  | 65 |  |  |  |  |
Benefits paid |  |  |  | (526) |  |  |  |  |
Unfunded status at end of the period |  |  |  | $ (2,924) |  |  | $ (2,924) |  |
Other Pension Plans, Defined Benefit | Change In Plan Assets | Predecessor |  |  |  |  |  |  |  |  |
Schedule Of Pension And Other Postretirement Benefits Changes In Benefit Obligation And Fair Value Of Plan Assets [Line Items] |  |  |  |  |  |  |  |  |
Employer contributions |  |  | 288 |  |  |  |  | 759 |
Participant contributions |  |  | 58 |  |  |  |  | 411 |
Benefits paid |  |  | (346) |  |  |  |  | (1,170) |
Unfunded status at end of the period |  |  | $ (4,817) |  |  |  |  | $ (4,811) |

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- Definition Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=112275985&loc=d3e4179-114921 + Details
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- Definition Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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- Definition Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=112275985&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920 + Details
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