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Summary of Inventories (Detail) - USD ($)
$ in Thousands
Jan. 31, 2016
Apr. 30, 2015
Inventory Disclosure [Abstract]    
Finished goods $ 27,562 $ 28,240
Finished parts 30,567 34,269
Work in process 8,047 7,492
Raw material 9,366 6,894
Total inventories $ 75,542 $ 76,895