Earnings Per Share (Details) (USD $)	3 Months Ended
	Oct. 31, 2013	Oct. 31, 2012
Earnings Per Share [Abstract]
Net income for basic calculation	$ 5,305,000	$ 7,435,000
Interest expense (net of tax) on 3.0% convertible senior notes	1,117,000	1,117,000
Numerator for diluted calculation	$ 6,422,000	$ 8,552,000
Denominator for basic calculation (in shares)	16,454,000	17,379,000
Dilutive effect on shares of stock-based awards (in shares)	75,000	159,000
Dilutive effect on shares of conversion of 3.0% convertible senior notes (in shares)	6,169,000	5,906,000
Denominator for diluted calculation (in shares)	22,698,000	23,444,000
Weighted average performance shares outstanding during the period that are excluded from EPS calculation	49,000	35,000
Reduction in weighted average shares as a result of the repurchase of common shares	14,000	0
Stock-Based Awards [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive equity-classified stock-based awards not included in calculation of diluted earnings per share (in shares)	2,750,000	2,382,000