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		6 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Earnings Per Share [Line Items]
Net income	$ 30,860	$ 33,553	$ 64,341	$ 71,051
Denominator for basic earnings per share for both Class A and Class B	52,018	53,320	52,020	53,232
Plus: Effect of dilutive stock options	264	507	268	549
Diluted	52,282	53,827	52,288	53,781
Class A nonvoting common stock
Earnings Per Share [Line Items]
Net earnings per share, basic	$ 0.59	$ 0.63	$ 1.24	$ 1.33
Net earnings per share, diluted	$ 0.59	$ 0.62	$ 1.23	$ 1.32
Common Class B [Member]
Earnings Per Share [Line Items]
Preferential dividends	$ 0	$ 0	$ 808	$ 828
Preferential dividends on dilutive stock options	0	0	4	(10)
Numerator for basic and diluted earnings per Class B Voting Common Share	$ 30,860	$ 33,553	$ 63,529	$ 70,213
Net earnings per share, basic	$ 0.59	$ 0.63	$ 1.22	$ 1.32
Net earnings per share, diluted	$ 0.59	$ 0.62	$ 1.21	$ 1.31