Losses Due to Repurchases Related to Repurchase Agreements (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2016	Apr. 30, 2015
Loss Contingencies [Line Items]
Cost of units repurchased	$ 1,961	$ 257	$ 2,969	$ 6,484
Realization of units resold	1,524	244	2,400	5,405
Losses due to repurchase	$ 437	$ 13	$ 569	$ 1,079

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