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		9 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2019	Apr. 30, 2018
Earnings Per Share [Line Items]
Net income	$ 34,781	$ 26,000	$ 94,645	$ 56,109
Denominator for basic earnings per share for both Class A and Class B	52,766	51,747	52,499	51,628
Plus: Effect of dilutive stock options	714	982	716	982
Denominator for diluted earnings per share for both Class A and Class B	53,480	52,729	53,215	52,610
Class A nonvoting common stock
Earnings Per Share [Line Items]
Net earnings per share, basic	$ 0.66	$ 0.50	$ 1.80	$ 1.09
Net earnings per share, diluted	$ 0.65	$ 0.49	$ 1.78	$ 1.07
Class B voting common stock
Earnings Per Share [Line Items]
Preferential dividends	$ 0	$ 0	$ 815	$ 799
Preferential dividends on dilutive stock options	0	0	13	(16)
Numerator for basic and diluted earnings per Class B Voting Common Share	$ 34,781	$ 26,000	$ 93,817	$ 55,294
Net earnings per share, basic	$ 0.66	$ 0.50	$ 1.79	$ 1.07
Net earnings per share, diluted	$ 0.65	$ 0.49	$ 1.76	$ 1.05