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Schedule of Other Changes in Plan Assets and Benefit Obligation Recognized (Detail) - USD ($) $ in Thousands | 4 Months Ended | 5 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jul. 31, 2017 | Dec. 31, 2017 | Mar. 31, 2017
Pension Plans, Defined Benefit |  |  |
Schedule Of Accumulated Benefit Obligations In Excess Of Fair Value Of Plan Assets And Amounts Recognized In Balance Sheet And In Other Comprehensive Income Loss [Line Items] |  |  |
Net (gain) loss |  | $ 1,939 |
Total recognized in other comprehensive (income) loss, before tax |  | 1,939 |
Net of tax |  | 1,939 |
Other Pension Plans, Defined Benefit |  |  |
Schedule Of Accumulated Benefit Obligations In Excess Of Fair Value Of Plan Assets And Amounts Recognized In Balance Sheet And In Other Comprehensive Income Loss [Line Items] |  |  |
Net (gain) loss |  | 325 |
Prior service (cost) credit |  | (1,861) |
Total recognized in other comprehensive (income) loss, before tax |  | (1,536) |
Net of tax |  | $ (1,536) |
Predecessor | Pension Plans, Defined Benefit |  |  |
Schedule Of Accumulated Benefit Obligations In Excess Of Fair Value Of Plan Assets And Amounts Recognized In Balance Sheet And In Other Comprehensive Income Loss [Line Items] |  |  |
Net (gain) loss | $ 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 | (21,204) |  | 2,036
Net of tax | (21,204) |  | 1,323
Predecessor | Other Pension Plans, Defined Benefit |  |  |
Schedule Of Accumulated Benefit Obligations In Excess Of Fair Value Of Plan Assets And Amounts Recognized In Balance Sheet And In Other Comprehensive Income Loss [Line Items] |  |  |
Net (gain) loss | 207 |  | (285)
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 | 20,524 |  | 5,199
Net of tax | $ 20,524 |  | $ 3,379

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- Definition Amount, after tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669686-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (i-k) -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580 + 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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