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, 2013	$ 404,062,000	$ 2,907,000	$ 363,888,000	$ 403,398,000	$ (366,131,000)
Treasury stock shares outstanding, beginning of period (in shares) at Jul. 31, 2013					12,608,501
Common stock shares issued, beginning of period (in shares) at Jul. 31, 2013		29,066,792
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-classified stock award compensation	3,051,000		3,051,000
Equity-classified stock awards issued	139,000		139,000
Proceeds from exercise of options	3,444,000	13,000	3,431,000
Proceeds from exercise of options (in shares)		131,175
Proceeds from issuance of employee stock purchase plan shares	670,000	3,000	667,000
Proceeds from issuance of employee stock purchase plan shares (in shares)		29,735
Common stock issued for net settlement of stock-based awards	(122,000)	1,000	(123,000)
Common stock issued for net settlement of stock-based awards (in shares)		8,984
Debt converted to shares of common stock	8,518,000	26,000	8,492,000
Debt converted to shares of common stock (in shares)		266,884
Cash dividends declared	(13,768,000)			(13,768,000)
Accrual of dividend equivalents	(80,000)			(80,000)
Net income tax shortfall from settlement of stock-based awards	(373,000)		(373,000)
Reversal of deferred tax assets associated with expired and unexercised stock-based awards	(1,933,000)		(1,933,000)
Repurchases of common stock	(58,122,000)				(58,122,000)
Repurchases of common stock (in shares)	1,851,303				1,851,303
Net income	17,163,000			17,163,000
Ending balance at Apr. 30, 2014	362,649,000	2,950,000	377,239,000	406,713,000	(424,253,000)
Treasury stock shares outstanding, end of period (in shares) at Apr. 30, 2014					14,459,804
Common stock shares issued, end of period (in shares) at Apr. 30, 2014		29,503,570
Beginning balance at Jul. 31, 2014	396,925,000	3,102,000	421,240,000	409,443,000	(436,860,000)
Treasury stock shares outstanding, beginning of period (in shares) at Jul. 31, 2014	14,857,582				14,857,582
Common stock shares issued, beginning of period (in shares) at Jul. 31, 2014	31,016,469	31,016,469
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-classified stock award compensation	3,642,000		3,642,000
Equity-classified stock awards issued	0
Proceeds from exercise of options	1,417,000	5,000	1,412,000
Proceeds from exercise of options (in shares)		49,200
Proceeds from issuance of employee stock purchase plan shares	707,000	2,000	705,000
Proceeds from issuance of employee stock purchase plan shares (in shares)		25,768
Common stock issued for net settlement of stock-based awards	(420,000)	6,000	(426,000)
Common stock issued for net settlement of stock-based awards (in shares)		60,120
Cash dividends declared	(14,567,000)			(14,567,000)
Accrual of dividend equivalents	(169,000)			(169,000)
Net income tax shortfall from settlement of stock-based awards	(248,000)		(248,000)
Reversal of deferred tax asset associated with debt converted to shares of common stock	(58,000)		(58,000)
Reversal of deferred tax assets associated with expired and unexercised stock-based awards	(12,000)		(12,000)
Repurchases of common stock	(4,989,000)				(4,989,000)
Repurchases of common stock (in shares)	175,735				175,735
Net income	17,770,000			17,770,000
Ending balance at Apr. 30, 2015	$ 399,998,000	$ 3,115,000	$ 426,255,000	$ 412,477,000	$ (441,849,000)
Treasury stock shares outstanding, end of period (in shares) at Apr. 30, 2015	15,033,317				15,033,317
Common stock shares issued, end of period (in shares) at Apr. 30, 2015	31,151,557	31,151,557