Income Taxes - Tax Cuts and Jobs Act (Details) - USD ($)		4 Months Ended	9 Months Ended	12 Months Ended
Dec. 22, 2017	Apr. 30, 2018	Jan. 31, 2018	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Income Taxes
U.S. federal statutory income tax rate (as a percent)	35.00%	21.00%	35.00%	21.00%	21.00%	30.40%
Deferred tax expense						$ 3,300,000

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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