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Income Taxes - Additional Information (Detail) - USD ($) |  | 3 Months Ended | 7 Months Ended | 8 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | ---
Dec. 22, 2017 | Jul. 31, 2018 | Jul. 31, 2017 | Jul. 31, 2018 | Dec. 31, 2017 | Apr. 30, 2019 | Apr. 30, 2018
Income Tax Contingency [Line Items] |  |  |  |  |  |  |
U.S federal income tax rate |  |  |  | 21.00% | 35.00% |  |
Tax reform, accounting complete | false |  |  |  |  |  |
Income tax benefit by effect of tax reform |  |  |  |  |  |  | $ 8,700,000
Deferred tax assets and liabilities enacted corporate federal tax rates, cash |  |  |  |  |  |  | $ 0
Effective income tax rate, provisions (benefit) |  | 33.30% | 49.60% |  |  |  |
Scenario, Forecast |  |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |  |
U.S federal income tax rate |  |  |  |  |  | 21.00% |

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