Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Apr. 30, 2018
Income Tax Disclosure [Abstract]
Unrecognized tax benefits	$ 7,255		$ 6,421
Unrecognized tax benefits that would impact effective tax rate	5,754
Accrued interest and penalties related to unrecognized tax benefits	223		$ 191
Net interest and penalties included in income tax expense	32	$ 19
Expected decrease in unrecognized tax benefits	$ 1,300