Unaudited Quarterly Financial Data (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, 2013	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2015		Jul. 31, 2014		Jul. 31, 2013
Selected Quarterly Financial Information [Abstract]
Net sales	$ 77,463,000	$ 71,633,000	$ 81,802,000	$ 76,391,000	$ 89,378,000	$ 88,905,000	$ 85,499,000	$ 83,368,000	$ 84,411,000	$ 69,856,000	$ 74,577,000	$ 90,953,000	$ 307,289,000		$ 347,150,000		$ 319,797,000
Gross profit	33,376,000	32,308,000	37,875,000	35,325,000	39,345,000	38,346,000	37,369,000	36,378,000	35,360,000	31,427,000	32,240,000	41,803,000	138,884,000		151,438,000		140,830,000
Net income	$ 5,475,000	$ 4,960,000	$ 7,585,000	$ 5,225,000	$ 7,988,000	$ 5,875,000	$ 5,983,000	$ 5,305,000	$ 5,156,000	$ 2,852,000	$ 2,365,000	$ 7,435,000	$ 23,245,000		$ 25,151,000		$ 17,808,000
Diluted income per share (in dollars per share)	$ 0.34	$ 0.30	$ 0.46	$ 0.32	$ 0.48	$ 0.32	$ 0.32	$ 0.28	$ 0.28	$ 0.17	$ 0.14	$ 0.36	$ 1.42	[1]	$ 1.37	[1]	$ 0.97	[1]

[1] The per share information is computed independently for each quarter and the full year based on the respective weighted average number of common shares outstanding. Therefore, income per share information for the full fiscal year may not equal the total of the quarters within the year.