Losses Due to Repurchases Related to Repurchase Agreements (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Oct. 31, 2014	Oct. 31, 2013
Loss Contingencies [Line Items]
Cost of units repurchased	$ 1,645	$ 123
Realization of units resold	1,440	101
Losses due to repurchase	$ 205	$ 22