Net Income per Common Share - Reconciliation of Numerator and Denominator of Basic and Diluted Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Oct. 31, 2020	Oct. 31, 2019
Earnings Per Share [Line Items]
Net income	$ 33,481	$ 37,498
Denominator for basic income per share for both Class A and Class B	52,021	53,143
Plus: Effect of dilutive equity awards	271	593
Denominator for diluted income per share for both Class A and Class B	52,292	53,736
Class A Nonvoting Common Stock
Earnings Per Share [Line Items]
Net income per share, basic	$ 0.64	$ 0.71
Net income per share, diluted	$ 0.64	$ 0.70
Class B Voting Common Stock
Earnings Per Share [Line Items]
Preferential dividends	$ (808)	$ (828)
Preferential dividends on dilutive stock options	(4)	(10)
Net income	$ 32,669	$ 36,660
Net income per share, basic	$ 0.63	$ 0.69
Net income per share, diluted	$ 0.62	$ 0.68