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Product Development Assets (Details) - USD ($)
$ in Thousands
Apr. 30, 2020
Apr. 30, 2019
Product Development Assets [Abstract]    
Product development assets $ 53,643 $ 62,470
Accumulated amortization 244,100 236,500
Book Composition Costs [Member]    
Product Development Assets [Abstract]    
Product development assets 18,744 19,197
Work in process 4,900 4,300
Software Costs [Member]    
Product Development Assets [Abstract]    
Product development assets 28,995 38,048
Content Development Costs [Member]    
Product Development Assets [Abstract]    
Product development assets $ 5,904 $ 5,225