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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%