Contractual Maturities of Debt Securities Classified as Trading (Detail) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2014	Apr. 30, 2013
Schedule of Trading Securities and Other Trading Assets [Line Items]
Due within one year	$ 7,646	$ 8,648
Due within two years	6,228	4,776
Due within three years	1,970	751
Due after three years	511	860
Total debt securities	$ 16,355	$ 15,035