Investments - Composition of income from securities transactions (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jul. 31, 2012	Jul. 31, 2011
Investment Income, Net [Abstract]
Dividend income	$ 26	$ 12
Interest income		8
Realized losses on securities available-for- sale (1)		(5)	[1]
Other		(4)
Income from securities transactions, net	$ 26	$ 11

[1] This amount was reclassified from Accumulated Other Comprehensive Income in the Consolidated Condensed Balance Sheets to the Consolidated Condensed Statements of Income.