Earnings Per Common Share - Computation (Details) - USD ($)	3 Months Ended		9 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2016	Apr. 30, 2015
Numerator for basic and diluted earnings per share:
Net income	$ 14,019,000	$ 12,356,000	$ 43,662,000	$ 34,680,000
Less income allocated to participating securities, basic	(115,000)	(105,000)	(359,000)	(323,000)
Net income available to common shareholders, basic	13,904,000	12,251,000	43,303,000	34,357,000
Less income allocated to participating securities, diluted	(115,000)	(105,000)	(359,000)	(323,000)
Net income available to common shareholders, diluted	$ 13,904,000	$ 12,251,000	$ 43,303,000	$ 34,357,000
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	41,363,548	41,187,720	41,335,488	41,114,830
Dilutive effect of stock options using the treasury stock method and the average market price for the period (in shares)	47,164	60,837	44,817	68,479
Denominator for diluted earnings per share - weighted average number of shares and common stock equivalents attributable to common stock	41,410,712	41,248,557	41,380,305	41,183,309
Earnings per share attributable to common stock:
Basic earnings per share (in dollars per share)	$ 0.34	$ 0.30	$ 1.05	$ 0.84
Diluted earnings per share (in dollars per share)	$ 0.34	$ 0.30	$ 1.05	$ 0.83