Investments - Carrying value and fair value of securities available-for-sale (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Oct. 31, 2013	Apr. 30, 2013
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 7,518	$ 6,295
Gross Unrealized Gains	1,082	767
Gross Unrealized Losses	(634)	(380)
Fair Value	7,966	6,682
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Cost	103	103
Gross Unrealized Gains	52	27
Gross Unrealized Losses	(16)	(16)
Fair Value	139	114
ETFs - equities
Schedule of Available-for-sale Securities [Line Items]
Cost	3,878	3,878
Gross Unrealized Gains	1,030	740
Gross Unrealized Losses	(8)
Fair Value	4,900	4,618
Inverse ETFs - equities
Schedule of Available-for-sale Securities [Line Items]
Cost	3,537	2,314
Gross Unrealized Gains
Gross Unrealized Losses	(610)	(364)
Fair Value	$ 2,927	$ 1,950