Losses Due to Repurchases Related to Repurchase Agreements (Detail) - USD ($) $ in Thousands	3 Months Ended
Oct. 31, 2016	Oct. 31, 2015
Loss Contingencies [Line Items]
Cost of units repurchased	$ 1,552	$ 819
Realization of units resold	1,544	687
Losses due to repurchase	$ 8	$ 132

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