Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	2 Months Ended	3 Months Ended	6 Months Ended		10 Months Ended
	Dec. 31, 2017	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017	Oct. 31, 2018
Operating Loss Carryforwards [Line Items]
Income tax expense (benefit)		$ (36)	$ (3,035)	$ 45
U.S. federal corporate tax rate	34.00%
Reduction of valuation allowance attributable to deferred tax assets			2,000
IPR&D
Operating Loss Carryforwards [Line Items]
Reduction in deferred tax liability			$ 1,000
Scenario Plan [Member]
Operating Loss Carryforwards [Line Items]
U.S. federal corporate tax rate					21.00%