Investments - Carrying value and fair value of securities available-for-sale (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 6,295	$ 3,749
Gross Unrealized Gains	767	215
Gross Unrealized Losses	(380)	(83)
Fair Value	6,682	3,881
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Cost	103	103
Gross Unrealized Gains	27	14
Gross Unrealized Losses	(16)	(5)
Fair Value	114	112
ETFs - equities
Schedule of Available-for-sale Securities [Line Items]
Cost	3,878	2,257
Gross Unrealized Gains	740	201
Gross Unrealized Losses		(5)
Fair Value	4,618	2,453
Inverse ETFs - equities
Schedule of Available-for-sale Securities [Line Items]
Cost	2,314	1,389
Gross Unrealized Gains
Gross Unrealized Losses	(364)	(73)
Fair Value	$ 1,950	$ 1,316