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Schedule of Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands | 3 Months Ended | 4 Months Ended | 5 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jul. 31, 2017 | Dec. 31, 2017 | Jun. 30, 2018 | Jun. 30, 2017 | Mar. 31, 2017
Pension Benefits |  |  |  |  |  |  |
Net Period Benefit Cost Assumptions [Line Items] |  |  |  |  |  |  |
Service cost | $ 41 |  |  | $ 546 | $ 71 |  |
Interest cost | 882 |  |  | 1,599 | 1,784 |  |
Expected return on plan assets | (482) |  |  | (882) | (964) |  |
Administrational expenses | 2 |  |  | 19 | 3 |  |
Payroll tax of net pension costs |  |  |  | 29 |  |  |
Amortization of net actuarial losses |  |  |  | 131 |  |  |
Curtailment gain |  |  |  | (99) |  |  |
Settlement loss recognized | 335 |  |  |  | 335 |  |
Net periodic pension cost | 778 |  |  | 1,343 | 1,229 |  |
Pension Benefits | Predecessor |  |  |  |  |  |  |
Net Period Benefit Cost Assumptions [Line Items] |  |  |  |  |  |  |
Service cost |  | $ 294 | $ 393 |  |  | $ 713 | $ 1,182
Interest cost |  | 984 | 1,313 |  |  | 1,975 | 3,814
Expected return on plan assets |  | (518) | (691) |  |  | (1,119) | (2,246)
Administrational expenses |  | 2 | 3 |  |  | 24 | 28
Payroll tax of net pension costs |  |  |  |  |  | 56 | 56
Amortization of net actuarial losses |  |  |  |  |  | 32 | 32
Recognized actuarial benefit |  | 561 | 748 |  |  | 1,008 | 1,785
Net periodic pension cost |  | 1,323 | 1,766 |  |  | 2,689 | 4,651
Other Benefits |  |  |  |  |  |  |
Net Period Benefit Cost Assumptions [Line Items] |  |  |  |  |  |  |
Service cost | 15 |  |  | 29 | 30 |  |
Interest cost | 29 |  |  | 75 | 58 |  |
Amortization of prior service cost | (75) |  |  |  | (150) |  |
Recognized actuarial benefit | 11 |  |  |  | 22 |  |
Net periodic pension cost | $ (20) |  |  | $ 104 | $ (40) |  |
Other Benefits | Predecessor |  |  |  |  |  |  |
Net Period Benefit Cost Assumptions [Line Items] |  |  |  |  |  |  |
Service cost |  | 17 | 23 |  |  | 38 | 81
Interest cost |  | 48 | 64 |  |  | 99 | 201
Amortization of prior service cost |  | (695) | (927) |  |  | (1,783) | (4,346)
Recognized actuarial benefit |  | (252) | (335) |  |  | (535) | (1,138)
Net periodic pension cost |  | $ (882) | $ (1,175) |  |  | $ (2,181) | $ (5,202)

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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 cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan. + 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 (h)(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 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)(1) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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