Stockholders' Equity (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Jul. 31, 2020	Jul. 31, 2019
Schedule Of Stockholders Equity [Line Items]
Additional paid-in capital	$ 332,121		$ 331,761
Retained earnings	726,546		704,456
Treasury Stock, Value	109,146		107,216
Accumulated other comprehensive loss	(69,668)		(66,477)	$ (71,254)
Stockholders' Equity Attributable to Parent	880,401	$ 876,535	863,072	850,774
Net income	33,481	37,498
Other Comprehensive Income (Loss), Net of Tax	(3,191)	(29)
Stock Issued During Period, Value, Stock Options Exercised	(2,456)	(3,857)
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	32	64
Share-based Payment Arrangement, Noncash Expense	3,574	3,618
Treasury Stock, Value, Acquired, Cost Method		0
Stock Repurchased During Period, Value	(2,720)
Payment of Ordinary Dividends, Common Stock Class A	(10,671)	(10,822)
Payment of Ordinary Dividends, Common Stock Class B	(720)	(711)
Common Stock [Member]
Schedule Of Stockholders Equity [Line Items]
Common Stock, Value, Issued	548	548	548	548
Additional Paid-in Capital [Member]
Schedule Of Stockholders Equity [Line Items]
Additional paid-in capital	332,121	327,241	331,761	329,969
Stock Issued During Period, Value, Stock Options Exercised	(3,246)	(6,410)
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	32	64
Share-based Payment Arrangement, Noncash Expense	3,574	3,618
Retained Earnings [Member]
Schedule Of Stockholders Equity [Line Items]
Retained earnings	726,546	663,808	704,456	637,843
Net income		37,498
Payment of Ordinary Dividends, Common Stock Class A	(10,671)	(10,822)
Payment of Ordinary Dividends, Common Stock Class B	(720)	(711)
Treasury Stock [Member]
Schedule Of Stockholders Equity [Line Items]
Treasury Stock, Value	(109,146)	(43,779)	(107,216)	$ (46,332)
Stock Issued During Period, Value, Stock Options Exercised	(790)	(2,553)
Treasury Stock, Value, Acquired, Cost Method		0
Stock Repurchased During Period, Value	2,720
AOCI Attributable to Parent [Member]
Schedule Of Stockholders Equity [Line Items]
Accumulated other comprehensive loss	(69,668)	(71,283)	$ (66,477)
Other Comprehensive Income (Loss), Net of Tax	$ (3,191)	$ (29)