Schedule of Change in Retained Earnings (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2015	Jan. 31, 2014
Retained Earnings Adjustments [Line Items]
Beginning Balance			$ 1,030,428
Net income	28,648	16,192	67,573	57,300
Dividends declared and paid			(28,824)
Ending Balance	$ 1,069,177		$ 1,069,177