Condensed Consolidated Statements of Stockholders' Equity (USD $)	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]
Beginning balance at Jul. 31, 2011	$ 629,180,000	$ 2,873,000	$ 355,001,000	$ 393,109,000	$ (121,803,000)
Treasury stock shares outstanding, beginning of period (in shares) at Jul. 31, 2011					4,508,445
Common stock shares issued, beginning of period (in shares) at Jul. 31, 2011		28,731,265
Equity-classified stock award compensation	853,000		853,000
Proceeds from exercise of options or units (in shares)		99,260
Proceeds from exercise of options	2,241,000	10,000	2,231,000
Proceeds from issuance of employee stock purchase plan shares (in shares)		12,018
Proceeds from issuance of employee stock purchase plan shares	287,000	1,000	286,000
Cash dividends declared	(6,102,000)			(6,102,000)
Net income tax shortfall from stock-based award exercises	(125,000)		(125,000)
Reversal of deferred tax assets associated with expired and unexercised stock-based awards	(1,021,000)		(1,021,000)
Repurchases of common stock (in shares)	2,717,393				2,717,393
Repurchases of common stock	(81,152,000)				(81,152,000)
Net income	12,601,000			12,601,000
Ending balance at Oct. 31, 2011	556,762,000	2,884,000	357,225,000	399,608,000	(202,955,000)
Common stock shares issued, end of period (in shares) at Oct. 31, 2011		28,842,543
Treasury stock shares outstanding, end of period (in shares) at Oct. 31, 2011					7,225,838
Beginning balance at Jul. 31, 2012	429,401,000	2,893,000	361,458,000	404,227,000	(339,177,000)
Treasury stock shares outstanding, beginning of period (in shares) at Jul. 31, 2012	11,564,059				11,564,059
Common stock shares issued, beginning of period (in shares) at Jul. 31, 2012	28,931,679	28,931,679
Equity-classified stock award compensation	750,000		750,000
Proceeds from exercise of options or units (in shares)	16,200	16,200
Proceeds from exercise of options	323,000	2,000	321,000
Proceeds from issuance of employee stock purchase plan shares (in shares)		10,549
Proceeds from issuance of employee stock purchase plan shares	248,000	1,000	247,000
Cash dividends declared	(4,784,000)			(4,784,000)
Net income tax shortfall from stock-based award exercises	(5,000)		(5,000)
Reversal of deferred tax assets associated with expired and unexercised stock-based awards	(2,892,000)		(2,892,000)
Repurchases of common stock (in shares)	0
Net income	7,435,000			7,435,000
Ending balance at Oct. 31, 2012	$ 430,476,000	$ 2,896,000	$ 359,879,000	$ 406,878,000	$ (339,177,000)
Common stock shares issued, end of period (in shares) at Oct. 31, 2012	28,958,428	28,958,428
Treasury stock shares outstanding, end of period (in shares) at Oct. 31, 2012	11,564,059				11,564,059