Note I - Stock-based Compensation - Stock Option Plan Comparison (Details)	6 Months Ended
	Oct. 31, 2016 shares
The 1997 Plan [Member]
Minimum exercise price as a percentage of fair market value at date of grant	100.00%
Last expiration date for outstanding options	Jul. 02, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant
Restated Option Plan [Member]
Minimum exercise price as a percentage of fair market value at date of grant	100.00%
Last expiration date for outstanding options	Aug. 10, 2026
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	276,500