FAIR VALUE OF FINANCIAL INSTRUMENTS - Additional Information (Detail) (Redeemed Available-for-Sale Securities, USD $)	3 Months Ended
Jul. 31, 2012	Jul. 31, 2011
Redeemed Available-for-Sale Securities
Schedule of Available-for-sale Securities [Line Items]
Redeemed available-for-sale securities	$ 2,000,000	$ 4,500,000
Realized gain	$ 6,800

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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