Commitments and Contingencies - Changes in Warranty Liability (Detail) (USD $)
In Thousands, unless otherwise specified
6 Months Ended
Jan. 31, 2015
Jan. 31, 2014
Movement in Standard Product Warranty Accrual [Roll Forward]    
Beginning Balance $ 943 $ 777
Changes to the provision 657 365
Obligations fulfilled during period (241) (240)
Ending Balance $ 1,359 $ 902