STOCK OPTION PLANS (Details) (USD $)	12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012
Award Options Granted [Line Items]
Options Outstanding at Shares under option	116,279	33,819
Options Outstanding at Weighted-average remaining life in years	3 years 10 months 17 days	1 year 8 months 1 day
Options Outstanding at Weighted-average Exercise Price	$ 6.70	$ 28.42
Options Exercisable at Shares under option	107,516	29,262
Options Exercisable at Weighted-average Exercise Price	$ 6.92	$ 29.45
2.52 - 5.88 [Member]
Award Options Granted [Line Items]
Options Outstanding at Shares under option	97,143
Options Outstanding at Weighted-average remaining life in years	4 years 5 months 5 days
Options Outstanding at Weighted-average Exercise Price	$ 4.09
Options Exercisable at Shares under option	88,571
Options Exercisable at Weighted-average Exercise Price	$ 4.13
16.59 - 39.90 [Member]
Award Options Granted [Line Items]
Options Outstanding at Shares under option	19,136
Options Outstanding at Weighted-average remaining life in years	1 year 25 days
Options Outstanding at Weighted-average Exercise Price	$ 19.94
Options Exercisable at Shares under option	18,945
Options Exercisable at Weighted-average Exercise Price	$ 19.93
16.59 - 24.71 [Member]
Award Options Granted [Line Items]
Options Outstanding at Shares under option		22,942
Options Outstanding at Weighted-average remaining life in years		2 years 25 days
Options Outstanding at Weighted-average Exercise Price		$ 19.71
Options Exercisable at Shares under option		18,386
Options Exercisable at Weighted-average Exercise Price		$ 19.18
39.9 - 44.31 [Member]
Award Options Granted [Line Items]
Options Outstanding at Shares under option		9,948
Options Outstanding at Weighted-average remaining life in years		10 months 28 days
Options Outstanding at Weighted-average Exercise Price		$ 43.67
Options Exercisable at Shares under option		9,947
Options Exercisable at Weighted-average Exercise Price		$ 43.67
71.75 - 84.70 [Member]
Award Options Granted [Line Items]
Options Outstanding at Shares under option		929
Options Outstanding at Weighted-average remaining life in years		1 month 20 days
Options Outstanding at Weighted-average Exercise Price		$ 80.32
Options Exercisable at Shares under option		929
Options Exercisable at Weighted-average Exercise Price		$ 80.32