Schedule of Change in Retained Earnings (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jan. 31, 2016	Jan. 31, 2015
Retained Earnings Adjustments [Line Items]
Beginning Balance	$ 1,172,432
Net income	95,165	$ 67,573
Dividends declared and paid	(31,485)
Ending Balance	$ 1,236,112