Earnings Per Common Share (Details) - USD ($)	3 Months Ended
	Oct. 31, 2015	Oct. 31, 2014
Numerator for basic and diluted earnings per share:
Net income	$ 14,254,000	$ 11,239,000
Less income allocated to participating securities, basic	(118,000)	(130,000)
Net income available to common shareholders, basic	14,136,000	11,109,000
Less income allocated to participating securities, diluted	(118,000)	(130,000)
Net income available to common shareholders, diluted	$ 14,136,000	$ 11,109,000
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	41,283,245	40,982,342
Dilutive effect of stock options using the treasury stock method and the average market price for the period (in shares)	38,875	87,993
Denominator for diluted earnings per share - weighted average number of shares and common stock equivalents attributable to common stock	41,322,120	41,070,335
Earnings per share attributable to common stock:
Basic earnings per share (in dollars per share)	$ 0.34	$ 0.27
Diluted earnings per share (in dollars per share)	$ 0.34	$ 0.27
Stock options excluded from weighted average dilutive common shares outstanding because their inclusion would have been antidilutive (in shares)	15,000	45,000