Note 4 - Preferred and Common Stock (Details) - Stock Option Activity (USD $)	12 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Note 4 - Preferred and Common Stock (Details) - Stock Option Activity [Line Items]
Outstanding- Number of option shares	712,024	712,024
Exercised- Number of option shares	(140,785,000)	(198,200,000)	(159,600,000)
Employee Stock Option [Member]
Note 4 - Preferred and Common Stock (Details) - Stock Option Activity [Line Items]
Outstanding- Number of option shares	712,024	854,809	1,053,509	775,109
Outstanding- Weighted average option exercise price	$ 36.73	$ 34.64	$ 32.59	$ 23.38
Granted- Number of option shares			441,000
Granted- Weighted average option exercise price			$ 44.39
Exercised- Number of option shares	(140,785)	(198,200)	(159,600)
Exercised- Weighted average option exercise price	$ 23.93	$ 23.82	$ 20.36
Forfeited- Number of option shares	(2,000)	(500)	(3,000)
Forfeited- Weighted average option exercise price	$ 44.39	$ 14.08	$ 36.19