Schedule of Change in Retained Earnings (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Oct. 31, 2014	Oct. 31, 2013
Retained Earnings Adjustments [Line Items]
Beginning Balance	$ 1,030,428
Net income	38,925	41,108
Dividends declared and paid	(14,412)
Ending Balance	$ 1,054,941