Schedule of Change in Retained Earnings (Detail) - USD ($) $ in Thousands	3 Months Ended
Oct. 31, 2016	Oct. 31, 2015
Retained Earnings Adjustments [Line Items]
Beginning Balance	$ 1,365,981
Net income	78,745	$ 50,497
Dividends declared but not paid	(17,352)
Ending Balance	$ 1,427,374

Amount of paid and unpaid cash, stock, and paid-in-kind (PIK) dividends declared, for example, but not limited to, common and preferred stock.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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