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Estimated Annual Amortization Expense Related to Amortizing Intangible Assets (Detail) - USD ($)
$ in Thousands
Apr. 30, 2018
Apr. 30, 2017
Finite-Lived Intangible Assets [Line Items]    
2019 $ 13,487  
2020 13,204  
2021 13,071  
2022 13,060  
2023 11,208  
Thereafter 32,474  
Amortized intangible assets, Net $ 96,504 $ 111,242