STOCKHOLDERS' EQUITY - Changes in stockholders' equity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2019	Apr. 30, 2018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (shares)			60,742,859
Beginning balance	$ 94,537	$ 128,697	$ 107,628	$ 62,971
Net income (loss)	(9,627)	(10,333)	(28,745)	44,248
Equity portion of convertible note	8,200		8,200
Preferred dividends	(525)	(529)
Issuance of common stock pursuant to employee stock purchase plan and stock option exercises	2	0	15	3
Restricted stock grants				47
Share-based compensation	404	2,260	1,174	9,657
Other comprehensive items	$ (605)	(1,437)	$ (426)	2,531
Ending balance (shares)	61,802,196		61,802,196
Ending balance	$ 92,386	$ 118,658	$ 92,386	118,658
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (shares)	61,797,807	60,205,946
Beginning balance	$ 618	$ 603	$ 608	$ 556
Issuance of common stock pursuant to employee stock purchase plan and stock option exercises (in shares)	4,389	4,258	13,794	6,703
Restricted stock grants (in shares)		528,896	1,045,543	5,225,806
Restricted stock grants		$ 5	$ 10	$ 52
Ending balance (shares)	61,802,196	60,739,100	61,802,196	60,739,100
Ending balance	$ 618	$ 608	$ 618	$ 608
Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	7,468,628	7,464,451	7,467,855	7,457,051
Equity portion of convertible note	8,200		8,200
Issuance of common stock pursuant to employee stock purchase plan and stock option exercises	2	0	15	3
Restricted stock grants		(5)	(10)
Share-based compensation	404	2,260	1,174	9,657
Ending balance	7,477,234	7,466,706	7,477,234	7,466,706
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(7,377,622)	(7,344,638)	(7,363,569)	(7,398,949)
Net income (loss)	(9,627)	(10,333)	(28,745)	44,248
Preferred dividends	(525)	(529)
Ending balance	(7,387,774)	(7,355,500)	(7,387,774)	(7,355,500)
Accumulated Other Comprehensive Income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	2,913	8,281	2,734	4,313
Other comprehensive items	(605)	(1,437)	(426)	2,531
Ending balance	$ 2,308	$ 6,844	$ 2,308	$ 6,844