Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	6 Months Ended
	Oct. 31, 2018	Oct. 31, 2017	Apr. 30, 2018
Income Tax Disclosure [Abstract]
Unrecognized tax benefits	$ 8,092		$ 6,421
Unrecognized tax benefits that would impact effective tax rate	6,415
Accrued interest and penalties related to unrecognized tax benefits	268		$ 191
Net interest and penalties included in income tax expense	77	$ 45
Expected decrease in unrecognized tax benefits	$ 1,300