Losses Due to Repurchases Related to Repurchase Agreements (Detail) - USD ($) $ in Thousands	3 Months Ended
Oct. 31, 2015	Oct. 31, 2014
Loss Contingencies [Line Items]
Cost of units repurchased	$ 819	$ 1,645
Realization of units resold	687	1,440
Losses due to repurchase	$ 132	$ 205

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