Accumulated Other Comprehensive Loss and Reclassifications (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 27, 2018	Jan. 28, 2017	Jan. 27, 2018	Jan. 28, 2017	Apr. 30, 2017
Accumulated other comprehensive loss
Total accumulated other comprehensive loss balance as of April 30, 2017			$ (127,000)
Total accumulated other comprehensive loss balance as of January 27, 2018	$ (25,000)		(25,000)		$ (127,000)
Other comprehensive income, tax			47,000		76,000
Change in foreign currency translation adjustments			0
Unrealized gain, tax portion	10,000	$ (23,000)	29,000	$ 6
Accumulated Other Comprehensive Loss
Accumulated other comprehensive loss
Total accumulated other comprehensive loss balance as of April 30, 2017			(127,000)
Change in foreign currency translation adjustments, net of $0 taxes	62,000		62,000
Unrealized gains, net of $19 of taxes			42,000
Total accumulated other comprehensive loss balance as of January 27, 2018	(23,000)		(23,000)		(127,000)
Foreign Currency Translation Adjustments
Accumulated other comprehensive loss
Change in foreign currency translation adjustments, net of $0 taxes	62,000		62,000
Total accumulated other comprehensive loss balance as of January 27, 2018	62,000		62,000
Available-For-Sale Securities.
Accumulated other comprehensive loss
Total accumulated other comprehensive loss balance as of April 30, 2017			(127,000)
Unrealized gains, net of $19 of taxes			42,000
Total accumulated other comprehensive loss balance as of January 27, 2018	$ (85,000)		$ (85,000)		$ (127,000)