Earnings Per Common Share (Details) - USD ($)	3 Months Ended								12 Months Ended
	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2015	Oct. 31, 2014	Jul. 31, 2014	Apr. 30, 2014	Jan. 31, 2014	Oct. 31, 2013	Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2013
Numerator for basic and diluted earnings per share:
Net income	$ 13,273,000	$ 12,356,000	$ 11,085,000	$ 11,239,000	$ 10,705,000	$ 10,249,000	$ 11,126,000	$ 11,185,000	$ 47,953,000	$ 43,265,000	$ 39,239,000
Less income allocated to participating securities, basic									(433,000)	(581,000)	(608,000)
Net income available to common shareholders, basic									47,520,000	42,684,000	38,631,000
Less income allocated to participating securities, diluted									(433,000)	(581,000)	(608,000)
Net income available to common shareholders, diluted									$ 47,520,000	$ 42,684,000	$ 38,631,000
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									41,139,467	40,751,629	40,267,885
Dilutive effect of stock options using the treasury stock method and the average market price for the period (in shares)									63,133	159,685	289,007
Denominator for diluted earnings per share - weighted average number of shares and common stock equivalents attributable to common stock									41,202,600	40,911,314	40,556,892
Earnings per share attributable to common stock:
Basic earnings per share (in dollars per share)	$ 0.32	$ 0.30	$ 0.27	$ 0.27	$ 0.26	$ 0.25	$ 0.27	$ 0.27	$ 1.16	$ 1.05	$ 0.96
Diluted earnings per share (in dollars per share)	$ 0.32	$ 0.30	$ 0.27	$ 0.27	$ 0.26	$ 0.25	$ 0.27	$ 0.27	$ 1.15	$ 1.04	$ 0.95