Stockholders' Equity - Schedule of change in retained earnings (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jan. 31, 2019	Jan. 31, 2018
Equity [Abstract]
Beginning Balance	$ 2,022,988
Cumulative effect of the adoption of ASU No. 2014-09, net of tax	(5,450)
Net income	8,536	$ 208,158
Dividends declared and paid	(41,189)
Ending Balance	$ 1,984,885