Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended		12 Months Ended
	Jan. 31, 2018	Oct. 31, 2017	Jan. 31, 2018	Jan. 31, 2017	Apr. 30, 2018	Apr. 30, 2017
Income Tax [Line Items]
Provisional income tax benefit due to change in tax rate	$ 167,000	$ 8,000
Unrecognized tax benefits	7,317		$ 7,317			$ 5,362
Unrecognized tax benefits that would impact effective tax rate	5,683		5,683
Accrued interest and penalties related to unrecognized tax benefits	254		254			$ 141
Net interest and penalties included in income tax expense			113	$ 104
Expected decrease in unrecognized tax benefits	$ 1,273		$ 1,273
Scenario, Forecast
Income Tax [Line Items]
Effective income tax rate					30.40%