Annual report pursuant to Section 13 and 15(d)

Intangible Assets (Detail)

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Intangible Assets (Detail) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Apr. 30, 2013
Apr. 30, 2012
Schedule Of Intangible Assets [Line Items]    
Weighted-Average Amortization Period (in years) 11 years  
Total amortized intangible assets $ 66,551 $ 23,751
Accumulated amortization (12,115) (7,128)
Total amortized intangible assets, net 54,436 16,623
Exchange rate fluctuations (49) (10)
Intangible assets 58,187 20,413
Trademarks
    
Schedule Of Intangible Assets [Line Items]    
Unamortized intangible assets 3,800 3,800
Intellectual Property
    
Schedule Of Intangible Assets [Line Items]    
Weighted-Average Amortization Period (in years) 20 years  
Total amortized intangible assets 22,900 11,400
Accumulated amortization (3,887) (2,241)
Total amortized intangible assets, net 19,013 9,159
Customer Lists
    
Schedule Of Intangible Assets [Line Items]    
Weighted-Average Amortization Period (in years) 10 years  
Total amortized intangible assets 34,899 6,399
Accumulated amortization (4,887) (2,748)
Total amortized intangible assets, net 30,012 3,651
Database Rights
    
Schedule Of Intangible Assets [Line Items]    
Weighted-Average Amortization Period (in years) 10 years  
Total amortized intangible assets 4,256 4,256
Accumulated amortization (1,500) (1,074)
Total amortized intangible assets, net 2,756 3,182
Trademarks
    
Schedule Of Intangible Assets [Line Items]    
Weighted-Average Amortization Period (in years) 4 years [1]  
Total amortized intangible assets 3,686 [1] 1,186 [1]
Accumulated amortization (1,331) [1] (698) [1]
Total amortized intangible assets, net 2,355 [1] 488 [1]
Noncompete Agreements
    
Schedule Of Intangible Assets [Line Items]    
Weighted-Average Amortization Period (in years) 5 years  
Total amortized intangible assets 810 510
Accumulated amortization (510) (367)
Total amortized intangible assets, net $ 300 $ 143
[1] During fiscal 2011, the Company wrote-off a trademark no longer in use with a net book value of $0.9 million, which is included as a component of general and administrative expenses in the accompanying consolidated statements of income.