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								12 Months Ended
	Jul. 31, 2019	Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017
Earnings Per Share [Line Items]
Earnings from continuing operations	$ 36,613	$ 34,781	$ 29,227	$ 30,637	$ 34,951	$ 26,000	$ 4,273	$ 25,836	$ 131,258	$ 91,060	$ 95,645
Cash dividends on Common Stock									$ 44,732	$ 42,873	$ 41,880
Denominator for basic earnings per share for both Class A and Class B									52,596	51,677	51,056
Plus: Effect of dilutive stock options									727	847	900
Denominator for diluted earnings per share for both Class A and Class B									53,323	52,524	51,956
Class A Nonvoting Common Stock [Member]
Earnings Per Share [Line Items]
Net income per share, basic	$ 0.69	$ 0.66	$ 0.56	$ 0.59	$ 0.67	$ 0.50	$ 0.08	$ 0.50	$ 2.50	$ 1.76	$ 1.87
Net income per share, diluted	$ 0.68	$ 0.65	$ 0.55	$ 0.58	$ 0.66	$ 0.49	$ 0.08	$ 0.49	$ 2.46	$ 1.73	$ 1.84
Class B Voting Common Stock [Member]
Earnings Per Share [Line Items]
Earnings from continuing operations									$ 130,430	$ 90,247	$ 94,843
Net income per share, basic									$ 2.48	$ 1.75	$ 1.86
Net income per share, diluted									$ 2.45	$ 1.72	$ 1.83
Preferential Dividends on Class A Nonvoting Common Stock [Member]
Earnings Per Share [Line Items]
Cash dividends on Common Stock									$ 815	$ 799	$ 788
Preferential Dividends on Dilutive Shares [Member]
Earnings Per Share [Line Items]
Cash dividends on Common Stock									$ 13	$ 14	$ 14