Earnings Per Common Share (Details) (USD $)	3 Months Ended
	Oct. 31, 2013	Oct. 31, 2012
Numerator for basic and diluted earnings per share:
Net income	$ 11,185,000	$ 9,576,000
Less income allocated to participating securities	(160,000)	(157,000)
Net income available to common shareholders	$ 11,025,000	$ 9,419,000
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	40,582,755	39,997,443
Dilutive effect of stock options using the treasury stock method and the average market price for the period (in shares)	192,105	364,238
Denominator for diluted earnings per share - weighted average number of shares and common stock equivalents attributable to common stock	40,774,860	40,361,681
Basic earnings per share attributable to common stock (in dollars per share)	$ 0.27	$ 0.24
Diluted earnings per share attributable to common stock (in dollars per share)	$ 0.27	$ 0.23
Stock options excluded from weighted average dilutive common shares outstanding because their inclusion would have been antidilutive (in shares)	30,000