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Summary of Phantom Stock Activity (Detail) - $ / shares | 4 Months Ended | 5 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jul. 31, 2017 | Dec. 31, 2017 | Dec. 31, 2018 | Mar. 31, 2017
Predecessor |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |
Weighted-average Grant-Date Fair Value, Beginning Balance Outstanding |  | $ 24.19 |  |  |  |  | $ 23.58
Weighted-average Grant-Date Fair Value, Ending Balance Outstanding |  |  |  |  |  |  | $ 24.19
Number of Shares Beginning Balance Outstanding |  | 350,838 |  |  |  |  | 363,630
Number of Shares Ending Balance Outstanding |  |  |  |  |  |  | 350,838
Phantom Stock Plan | Series A Warrants |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |
Weighted-average Grant-Date Fair Value, Beginning Balance Outstanding |  |  |  |  |  | $ 1.00 |
Weighted-average Grant-Date Fair Value, Issuance of Successor phantom stock | [1] |  |  | $ 1.00 |  |  |
Weighted-average Grant-Date Fair Value, Vested |  |  |  |  |  | 1.00 |
Weighted-average Grant-Date Fair Value, Cancelled/forfeited |  |  |  | 1.00 |  |  |
Weighted-average Grant-Date Fair Value, Cancelled | [2] |  |  |  |  | 1.00 |
Weighted-average Grant-Date Fair Value, Ending Balance Outstanding |  |  |  | $ 1.00 |  | $ 1.00 |
Number of Shares Beginning Balance Outstanding |  |  |  |  |  | 21,934 |
Number of Shares, Issuance of Successor phantom stock | [1] |  |  | 22,963 |  |  |
Number of Shares, Vested |  |  |  |  |  | (13,009) |
Number of Shares, Cancelled/forfeited |  |  |  | (1,029) |  |  |
Weighted-average Grant-Date Fair Value, Cancelled | [2] |  |  |  |  | (1,275) |
Number of Shares Ending Balance Outstanding |  |  |  | 21,934 |  | 7,650 |
Phantom Stock Plan | Series B Warrants |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |
Weighted-average Grant-Date Fair Value, Beginning Balance Outstanding |  |  |  |  |  | $ 0.98 |
Weighted-average Grant-Date Fair Value, Issuance of Successor phantom stock | [1] |  |  | $ 0.98 |  |  |
Weighted-average Grant-Date Fair Value, Vested |  |  |  |  |  | 0.98 |
Weighted-average Grant-Date Fair Value, Cancelled/forfeited |  |  |  | 0.98 |  |  |
Weighted-average Grant-Date Fair Value, Cancelled | [2] |  |  |  |  | 0.98 |
Weighted-average Grant-Date Fair Value, Ending Balance Outstanding |  |  |  | $ 0.98 |  | $ 2.94 |
Number of Shares Beginning Balance Outstanding |  |  |  |  |  | 23,712 |
Number of Shares, Issuance of Successor phantom stock | [1] |  |  | 24,824 |  |  |
Number of Shares, Vested |  |  |  |  |  | (14,064) |
Number of Shares, Cancelled/forfeited |  |  |  | (1,112) |  |  |
Weighted-average Grant-Date Fair Value, Cancelled | [2] |  |  |  |  | (1,379) |
Number of Shares Ending Balance Outstanding |  |  |  | 23,712 |  | 8,269 |
Phantom Stock Plan | Time Based Restricted Stock Awards |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |
Weighted-average Grant-Date Fair Value, Beginning Balance Outstanding |  |  |  |  |  | $ 308.24 |
Weighted-average Grant-Date Fair Value, Issuance of Successor phantom stock | [1] |  |  | $ 308.19 |  |  |
Weighted-average Grant-Date Fair Value, Vested |  |  |  |  |  | 360.14 |
Weighted-average Grant-Date Fair Value, Cancelled/forfeited |  |  |  | 307.31 |  |  |
Weighted-average Grant-Date Fair Value, Cancelled | [2] |  |  |  |  | 240.39 |
Weighted-average Grant-Date Fair Value, Ending Balance Outstanding |  |  |  | $ 308.24 |  | $ 226.50 |
Number of Shares Beginning Balance Outstanding |  |  |  |  |  | 13,526 |
Number of Shares, Issuance of Successor phantom stock | [1] |  |  | 14,160 |  |  |
Number of Shares, Vested |  |  |  |  |  | (8,223) |
Number of Shares, Cancelled/forfeited |  |  |  | (634) |  |  |
Weighted-average Grant-Date Fair Value, Cancelled | [2] |  |  |  |  | (786) |
Number of Shares Ending Balance Outstanding |  |  |  | 13,526 |  | 4,517 |
Phantom Stock Plan | Time Based Restricted Stock Awards | Predecessor |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |
Weighted-average Grant-Date Fair Value, Beginning Balance Outstanding |  | $ 9.74 |  | $ 9.77 | [1] |  | $ 10.83
Weighted-average Grant-Date Fair Value, Vested |  |  |  |  |  |  | 12.29
Weighted-average Grant-Date Fair Value, Cancelled/forfeited |  |  |  |  |  |  | 13.52
Weighted-average Grant-Date Fair Value, Cancelled | [2] | 9.70 |  |  |  |  |
Weighted-average Grant-Date Fair Value, forfeited |  | 10.08 |  |  |  |  |
Weighted-average Grant-Date Fair Value, Ending Balance Outstanding |  | $ 9.77 | [1] |  |  |  | $ 9.74
Number of Shares Beginning Balance Outstanding |  | 946,150 |  | 444,838 | [1] |  | 1,599,829
Number of Shares, Vested |  |  |  |  |  |  | (585,426)
Number of Shares, Cancelled/forfeited |  |  |  |  |  |  | (68,253)
Weighted-average Grant-Date Fair Value, Cancelled | [2] | (484,446) |  |  |  |  |
Weighted-average Grant-Date Fair Value, forfeited |  | (16,866) |  |  |  |  |
Number of Shares Ending Balance Outstanding |  | 444,838 | [1] |  |  |  | 946,150
[1] | Upon emergence from Chapter 11 bankruptcy, all outstanding phantom stock units held by non-officer employees were converted by the same conversion ratio applied to the common shares upon emergence. Every 31.4143 phantom stock units converted into one phantom stock unit post emergence which is valued to the new common stock. In addition, each post emergence phantom stock unit received 1.6216 phantom series A warrants and 1.7531 phantom series B warrants. Both warrant series have time-based vesting and follow the vesting schedule of the underlying phantom stock unit.
[2] | Prior to emergence from Chapter 11 bankruptcy, all officer-held phantom stock units were cancelled.

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- Definition Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(3) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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