Earnings Per Common Share (Details) (USD $)	3 Months Ended		9 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2015	Apr. 30, 2014
Numerator for basic and diluted earnings per share:
Net income	$ 12,356,000	$ 10,249,000	$ 34,680,000	$ 32,560,000
Less income allocated to participating securities, basic	(105,000)	(135,000)	(323,000)	(444,000)
Net income available to common shareholders, basic	12,251,000	10,114,000	34,357,000	32,116,000
Less income allocated to participating securities, diluted	(105,000)	(135,000)	(323,000)	(444,000)
Net income available to common shareholders, diluted	$ 12,251,000	$ 10,114,000	$ 34,357,000	$ 32,116,000
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	41,187,720	40,813,778	41,114,830	40,716,018
Dilutive effect of stock options using the treasury stock method and the average market price for the period (in shares)	60,837	143,319	68,479	174,107
Denominator for diluted earnings per share - weighted average number of shares and common stock equivalents attributable to common stock	41,248,557	40,957,097	41,183,309	40,890,125
Earnings per share attributable to common stock:
Basic earnings per share (in dollars per share)	$ 0.30	$ 0.25	$ 0.84	$ 0.79
Diluted earnings per share (in dollars per share)	$ 0.30	$ 0.25	$ 0.83	$ 0.79
Stock options excluded from weighted average dilutive common shares outstanding because their inclusion would have been antidilutive (in shares)		30,000