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, 2017	Oct. 31, 2016
Earnings Per Share [Line Items]
Net Income (Loss) Attributable to Parent	$ 25,836	$ 22,553
Denominator for basic earnings for both Class A and Class B	51,440	50,634
Plus: Effect of dilutive stock options	943	821
Denominator for diluted earnings per share for both Class A and Class B	52,383	51,455
Class A Nonvoting Common Stock
Earnings Per Share [Line Items]
Net earnings per share, basic	$ 0.50	$ 0.45
Net earnings per share, diluted	$ 0.49	$ 0.44
Class B Voting Common Stock
Earnings Per Share [Line Items]
Preferential dividends	$ (799)	$ (788)
Preferential dividends on dilutive stock options	(16)	(14)
Earnings from continuing operations	$ 25,021	$ 21,751
Net earnings per share, basic	$ 0.49	$ 0.43
Net earnings per share, diluted	$ 0.48	$ 0.42