Income Taxes - Additional Information (Details) - USD ($)	2 Months Ended	3 Months Ended		6 Months Ended
	Dec. 31, 2017	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2019	Apr. 30, 2018
Operating Loss Carryforwards [Line Items]
Income tax expense (benefit)		$ 69,000	$ 0	$ 69,000	$ (3,035,000)
U.S. federal corporate tax rate	34.00%			21.00%
Reduction of valuation allowance attributable to deferred tax assets				$ 2,000,000
IPR&D
Operating Loss Carryforwards [Line Items]
Reduction in deferred tax liability				$ 1,000,000