Investments - Composition of income from securities transactions (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Investment Income, Net [Abstract]
Dividend income	$ 36	$ 30	$ 72	$ 57
Other	(2)			(1)
Total income from securities transactions, net	$ 34	$ 30	$ 72	$ 56