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Commitments and Contingencies - Additional Information (Detail) (USD $)
12 Months Ended
Apr. 30, 2014
Apr. 30, 2013
Apr. 30, 2012
Commitment And Contingencies [Line Items]      
Rental expense for operating leases $ 841,000 $ 854,000 $ 906,000
Employee contribution percentage 60.00%    
Headquarters in Atlanta, GA
     
Commitment And Contingencies [Line Items]      
Operating lease rental income 574,000 418,000 349,000
Various Operating Leases
     
Commitment And Contingencies [Line Items]      
Operating lease rental income $ 230,000 $ 225,000 $ 204,000