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Development Project Charges - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 12 Months Ended
Oct. 31, 2011
Apr. 30, 2012
Apr. 30, 2013
Collaborative Arrangements Non collaborative Arrangements And Business Acquisitions Transactions [Line Items]      
Deferred costs associated with development projects $ 131 $ 131  
Deferred project costs   $ 1,163 $ 1,644