Earnings Per Common Share (Details) (USD $)	3 Months Ended		6 Months Ended
	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2014	Jan. 31, 2013
Numerator for basic and diluted earnings per share:
Net income	$ 11,126,000	$ 10,452,000	$ 22,311,000	$ 20,028,000
Less income allocated to participating securities	(149,000)	(160,000)	(309,000)	(317,000)
Net income available to common shareholders	$ 10,977,000	$ 10,292,000	$ 22,002,000	$ 19,711,000
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	40,754,707	40,247,046	40,668,731	40,122,245
Dilutive effect of stock options using the treasury stock method and the average market price for the period (in shares)	183,995	314,004	188,201	338,331
Denominator for diluted earnings per share - weighted average number of shares and common stock equivalents attributable to common stock	40,938,702	40,561,050	40,856,932	40,460,576
Basic earnings per share attributable to common stock (in dollars per share)	$ 0.27	$ 0.26	$ 0.54	$ 0.49
Diluted earnings per share attributable to common stock (in dollars per share)	$ 0.27	$ 0.25	$ 0.54	$ 0.49
Stock options excluded from weighted average dilutive common shares outstanding because their inclusion would have been antidilutive (in shares)	30,000	52,500