Earnings Per Share (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average performance shares outstanding during the period that are excluded from EPS Calculation (in shares)	259,000	237,000	211,000	229,000
Net income for basic calculation	$ 15,761,000	$ 6,585,000	$ 14,101,000	$ 4,096,000
Numerator for diluted calculation	$ 15,761,000	$ 6,585,000	$ 14,101,000	$ 4,096,000
Denominator for basic calculation (in shares)	23,816,000	23,428,000	23,805,000	23,406,000
Effect of dilutive securities: Stock-based awards (in shares)	137,000	17,000	137,000	21,000
Denominator for diluted calculation (in shares)	23,953,000	23,445,000	23,942,000	23,427,000
Stock options, performance shares (with the performance conditions satisfied), RSUs and restricted stock
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)	1,812,000	2,173,000	1,821,000	2,305,000