Consolidated Statements of Stockholders' Equity - USD ($)	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock
Beginning balance at Jul. 31, 2014	$ 396,925,000	$ 3,102,000	$ 421,240,000	$ 409,443,000	$ (436,860,000)
Common stock shares issued, beginning of period (in shares) at Jul. 31, 2014		31,016,469
Treasury stock shares outstanding, beginning of period (in shares) at Jul. 31, 2014					14,857,582
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-classified stock award compensation	4,387,000		4,387,000
Proceeds from exercise of options	1,439,000	$ 5,000	1,434,000
Proceeds from exercise of options (in shares)		50,000
Proceeds from issuance of employee stock purchase plan shares	917,000	$ 3,000	914,000
Proceeds from issuance of employee stock purchase plan shares (in shares)		34,310
Common stock issued for net settlement of stock-based awards	(473,000)	$ 7,000	(480,000)
Common stock issued for net settlement of stock-based awards (in shares)		64,622
Cash dividends declared	(19,406,000)			(19,406,000)
Accrual of dividend equivalents	(224,000)			(224,000)
Net income tax shortfall from settlement of stock-based awards	(341,000)		(341,000)
Reversal of deferred tax assets 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	(13,000)		(13,000)
Repurchases of common stock	(4,989,000)				$ (4,989,000)
Repurchases of common stock (in shares)					175,735
Net income (loss)	23,245,000			23,245,000
Ending balance at Jul. 31, 2015	401,409,000	$ 3,117,000	427,083,000	413,058,000	$ (441,849,000)
Common stock shares issued, end of period (in shares) at Jul. 31, 2015		31,165,401
Treasury stock shares outstanding, end of period (in shares) at Jul. 31, 2015					15,033,317
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued from equity offering, net of issuance costs	94,070,000	$ 715,000	93,355,000
Common stock issued from equity offering, net of issuance costs (in shares)		7,145,000
Equity-classified stock award compensation	4,076,000		4,076,000
Proceeds from issuance of employee stock purchase plan shares	676,000	$ 4,000	672,000
Proceeds from issuance of employee stock purchase plan shares (in shares)		45,319
Common stock issued for net settlement of stock-based awards	(105,000)	$ 1,000	(106,000)
Common stock issued for net settlement of stock-based awards (in shares)		12,277
Cash dividends declared	(21,549,000)			(21,549,000)
Accrual of dividend equivalents	(155,000)			(155,000)
Net income tax shortfall from settlement of stock-based awards	(27,000)		(27,000)
Reversal of deferred tax assets associated with expired and unexercised stock-based awards	$ (256,000)		(256,000)
Repurchases of common stock (in shares)	0
Net income (loss)	$ (7,738,000)			(7,738,000)
Ending balance at Jul. 31, 2016	$ 470,401,000	$ 3,837,000	524,797,000	383,616,000	$ (441,849,000)
Common stock shares issued, end of period (in shares) at Jul. 31, 2016	38,367,997	38,367,997
Treasury stock shares outstanding, end of period (in shares) at Jul. 31, 2016	15,033,317				15,033,317
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-classified stock award compensation	$ 8,467,000		8,467,000
Proceeds from issuance of employee stock purchase plan shares	694,000	$ 7,000	687,000
Proceeds from issuance of employee stock purchase plan shares (in shares)		64,367
Issuance of restricted stock, net	0	$ (14,000)	14,000
Issuance of restricted stock, net (in shares)		144,988
Common stock issued for net settlement of stock-based awards	(262,000)	$ 4,000	(266,000)
Common stock issued for net settlement of stock-based awards (in shares)		42,115
Cash dividends declared	(14,034,000)			(14,034,000)
Accrual of dividend equivalents	(273,000)			(273,000)
Net income tax shortfall from settlement of stock-based awards	(248,000)		(248,000)
Reversal of deferred tax assets associated with expired and unexercised stock-based awards	$ (422,000)		(422,000)
Repurchases of common stock (in shares)	0
Net income (loss)	$ 15,827,000			15,827,000
Ending balance at Jul. 31, 2017	$ 480,150,000	$ 3,862,000	$ 533,001,000	$ 385,136,000	$ (441,849,000)
Common stock shares issued, end of period (in shares) at Jul. 31, 2017	38,619,467	38,619,467
Treasury stock shares outstanding, end of period (in shares) at Jul. 31, 2017	15,033,317				15,033,317