Losses Due to Repurchases under Repurchase Agreements (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2012
Loss Contingencies [Line Items]
Cost of units repurchased	$ 1,386	$ 6,926	$ 2,881
Realization of units resold	1,098	6,020	2,521
Losses due to repurchase	$ 288	$ 906	$ 360