BUSINESS SEGMENTS (Summary of Certain Financial Information from Continuing Operations by Reportable Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 29, 2020	Feb. 28, 2019	Feb. 29, 2020	Feb. 28, 2019	Aug. 31, 2019
Segment Reporting Information [Line Items]
Net sales	$ 1,340,963	$ 1,402,783	$ 2,725,671	$ 2,680,125
Adjusted EBITDA from continuing operations	137,721	69,333	297,526	134,869
Total assets	3,907,938		3,907,938		$ 3,758,771
Continuing Operations
Segment Reporting Information [Line Items]
Net sales	1,340,963	1,402,783	2,725,671	2,680,125
Americas Recycling
Segment Reporting Information [Line Items]
Net sales	179,535	225,888	351,686	466,069
Americas Mills
Segment Reporting Information [Line Items]
Net sales	471,367	472,795	945,559	846,466
Americas Fabrication
Segment Reporting Information [Line Items]
Net sales	510,381	526,678	1,080,758	961,236
International Mill
Segment Reporting Information [Line Items]
Net sales	179,656	174,945	344,696	401,618
Corporate
Segment Reporting Information [Line Items]
Net sales	24	2,477	2,972	4,736
Intersegment | Continuing Operations
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Intersegment | Americas Recycling
Segment Reporting Information [Line Items]
Net sales	68,549	61,187	118,659	123,015
Intersegment | Americas Mills
Segment Reporting Information [Line Items]
Net sales	260,673	301,914	555,374	530,096
Intersegment | Americas Fabrication
Segment Reporting Information [Line Items]
Net sales	1,367	4,158	2,837	6,711
Intersegment | International Mill
Segment Reporting Information [Line Items]
Net sales	423	253	772	604
Intersegment | Corporate
Segment Reporting Information [Line Items]
Net sales	(331,012)	(367,512)	(677,642)	(660,426)
Segments | Continuing Operations
Segment Reporting Information [Line Items]
Net sales	1,340,963	1,402,783	2,725,671	2,680,125
Adjusted EBITDA from continuing operations	137,721	69,333	297,526	134,869
Total assets	3,907,938		3,907,938		3,758,771
Segments | Americas Recycling
Segment Reporting Information [Line Items]
Net sales	248,084	287,075	470,345	589,084
Adjusted EBITDA from continuing operations	5,754	10,124	9,171	25,558
Total assets	261,611		261,611		257,517
Segments | Americas Mills
Segment Reporting Information [Line Items]
Net sales	732,040	774,709	1,500,933	1,376,562
Adjusted EBITDA from continuing operations	125,691	112,396	280,716	226,269
Total assets	1,680,295		1,680,295		1,667,366
Segments | Americas Fabrication
Segment Reporting Information [Line Items]
Net sales	511,748	530,836	1,083,595	967,947
Adjusted EBITDA from continuing operations	16,060	(49,578)	33,541	(86,574)
Total assets	1,065,676		1,065,676		1,106,420
Segments | International Mill
Segment Reporting Information [Line Items]
Net sales	180,079	175,198	345,468	402,222
Adjusted EBITDA from continuing operations	13,451	20,537	24,810	53,316
Total assets	521,678		521,678		464,177
Segments | Corporate
Segment Reporting Information [Line Items]
Net sales	(330,988)	(365,035)	(674,670)	(655,690)
Adjusted EBITDA from continuing operations	(23,235)	$ (24,146)	(50,712)	$ (83,700)
Total assets	$ 378,678		$ 378,678		$ 263,291