Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Accumulated other comprehensive loss
Balance, net of $0 deferred taxes, as of April 30, 2019	$ 2
Balance, net of $0 deferred taxes, as of January 25, 2020	328	$ 2
Unrealized gain, tax portion	14	51	$ 25
Available-For-Sale Securities.
Accumulated other comprehensive loss
Unrealized gains, net of $51 of taxes	50
Balance, net of $0 deferred taxes, as of January 25, 2020	50
Foreign Currency Translation Adjustments
Accumulated other comprehensive loss
Balance, net of $0 deferred taxes, as of April 30, 2019	2
Change in foreign currency translation adjustments, net of $0 taxes	276
Balance, net of $0 deferred taxes, as of January 25, 2020	278	2
Accumulated Other Comprehensive Income
Accumulated other comprehensive loss
Balance, net of $0 deferred taxes, as of April 30, 2019	2
Change in foreign currency translation adjustments, net of $0 taxes	276
Unrealized gains, net of $51 of taxes	50
Balance, net of $0 deferred taxes, as of January 25, 2020	$ 328	$ 2