Note 5 - Disclosure of Compensation Related Costs, Stock Based Payments (Details) - Stock Option Activity (Employee Stock Option [Member], USD $)	9 Months Ended
	Jan. 31, 2014
Employee Stock Option [Member]
Note 5 - Disclosure of Compensation Related Costs, Stock Based Payments (Details) - Stock Option Activity [Line Items]
Outstanding at April 30, 2013	854,809
Outstanding at April 30, 2013 (in Dollars per share)	$ 34.64
Outstanding at January 31, 2014	731,374
Outstanding at January 31, 2014 (in Dollars per share)	$ 36.38
Granted	0
Granted (in Dollars per share)	$ 0
Exercised	(121,435)
Exercised (in Dollars per share)	$ 23.98
Forfeited	(2,000)
Forfeited (in Dollars per share)	$ 44.39