BUSINESS SEGMENTS (Summary of Certain Financial Information from Continuing Operations by Reportable Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	May 31, 2020	May 31, 2019	May 31, 2020	May 31, 2019	Aug. 31, 2019
Segment Reporting Information [Line Items]
Net sales	$ 1,341,683	$ 1,605,872	$ 4,067,354	$ 4,285,997
Adjusted EBITDA from continuing operations	146,782	143,971	444,308	278,840
Total assets	3,954,887		3,954,887		$ 3,758,771
Continuing Operations
Segment Reporting Information [Line Items]
Net sales	1,341,683	1,605,872	4,067,354	4,285,997
Americas Recycling
Segment Reporting Information [Line Items]
Net sales	148,021	228,786	499,707	694,855
Americas Mills
Segment Reporting Information [Line Items]
Net sales	451,278	536,035	1,396,837	1,382,501
Americas Fabrication
Segment Reporting Information [Line Items]
Net sales	567,782	629,510	1,648,540	1,590,746
International Mill
Segment Reporting Information [Line Items]
Net sales	173,465	209,022	518,161	610,640
Corporate
Segment Reporting Information [Line Items]
Net sales	1,137	2,519	4,109	7,255
Intersegment | Continuing Operations
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Intersegment | Americas Recycling
Segment Reporting Information [Line Items]
Net sales	55,134	60,229	173,793	183,244
Intersegment | Americas Mills
Segment Reporting Information [Line Items]
Net sales	289,534	330,868	844,908	860,964
Intersegment | Americas Fabrication
Segment Reporting Information [Line Items]
Net sales	1,466	3,537	4,303	10,248
Intersegment | International Mill
Segment Reporting Information [Line Items]
Net sales	352	343	1,124	947
Intersegment | Corporate
Segment Reporting Information [Line Items]
Net sales	(346,486)	(394,977)	(1,024,128)	(1,055,403)
Segments | Continuing Operations
Segment Reporting Information [Line Items]
Net sales	1,341,683	1,605,872	4,067,354	4,285,997
Adjusted EBITDA from continuing operations	146,782	143,971	444,308	278,840
Total assets	3,954,887		3,954,887		3,758,771
Segments | Americas Recycling
Segment Reporting Information [Line Items]
Net sales	203,155	289,015	673,500	878,099
Adjusted EBITDA from continuing operations	(1,664)	12,331	7,507	37,889
Total assets	216,270		216,270		257,517
Segments | Americas Mills
Segment Reporting Information [Line Items]
Net sales	740,812	866,903	2,241,745	2,243,465
Adjusted EBITDA from continuing operations	133,174	158,114	413,890	384,383
Total assets	1,609,574		1,609,574		1,667,366
Segments | Americas Fabrication
Segment Reporting Information [Line Items]
Net sales	569,248	633,047	1,652,843	1,600,994
Adjusted EBITDA from continuing operations	31,896	(23,289)	65,437	(109,863)
Total assets	1,052,324		1,052,324		1,106,420
Segments | International Mill
Segment Reporting Information [Line Items]
Net sales	173,817	209,365	519,285	611,587
Adjusted EBITDA from continuing operations	14,270	24,120	39,080	77,436
Total assets	506,192		506,192		464,177
Segments | Corporate
Segment Reporting Information [Line Items]
Net sales	(345,349)	(392,458)	(1,020,019)	(1,048,148)
Adjusted EBITDA from continuing operations	(30,894)	$ (27,305)	(81,606)	$ (111,005)
Total assets	$ 570,527		$ 570,527		$ 263,291