Schedule of Change in Retained Earnings (Detail) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2015	Oct. 31, 2014
Retained Earnings Adjustments [Line Items]
Beginning Balance	$ 1,172,432
Net income	50,497	$ 38,925
Dividends declared and paid	(15,743)
Ending Balance	$ 1,207,186