Earnings Per Common Share - Computation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017
Numerator for basic and diluted earnings per share:
Net income	$ 18,736	$ 17,511	$ 74,153	$ 54,381
Less income allocated to participating securities	(59)	(98)	(281)	(335)
Net income available to common shareholders	$ 18,677	$ 17,413	$ 73,872	$ 54,046
Denominator for basic and diluted earnings per share, as adjusted for participating securities:
Denominator for basic earnings per share - weighted average number of shares outstanding attributable to common stock (in shares)	41,580,387	41,489,587	41,559,312	41,459,067
Dilutive effect of stock awards using the treasury stock method and the average market price for the year (in shares)	69,134	75,431	63,642	74,420
Denominator for diluted earnings per share - weighted average number of shares and common stock equivalents attributable to common stock (in shares)	41,649,521	41,565,018	41,622,954	41,533,487
Earnings per share attributable to common stock:
Basic earnings per share (in dollars per share)	$ 0.45	$ 0.42	$ 1.78	$ 1.30
Diluted earnings per share (in dollars per share)	$ 0.45	$ 0.42	$ 1.77	$ 1.30
Stock options excluded from weighted average dilutive common shares outstanding because their inclusion would have been anti-dilutive (in shares)	0	0	0	0