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, 2019	May 31, 2018	May 31, 2019	May 31, 2018	Aug. 31, 2018
Segment Reporting Information [Line Items]
Net sales	$ 1,605,872	$ 1,204,484	$ 4,285,997	$ 3,335,285
Adjusted EBITDA from continuing operations	143,971	101,032	278,840	245,175
Total assets	3,767,010		3,767,010		$ 3,328,304
Continuing Operations
Segment Reporting Information [Line Items]
Net sales	1,605,872	1,204,484	4,285,997	3,335,285
Adjusted EBITDA from continuing operations	143,971	101,032	278,840	245,175
Total assets	3,767,010		3,767,010		3,328,304
Americas Recycling
Segment Reporting Information [Line Items]
Net sales	228,786	292,679	694,855	832,448
Adjusted EBITDA from continuing operations	12,331	19,477	37,889	51,698
Total assets	262,620		262,620		291,838
Americas Mills
Segment Reporting Information [Line Items]
Net sales	536,035	332,459	1,382,501	841,895
Adjusted EBITDA from continuing operations	158,114	89,590	384,383	194,975
Total assets	1,682,255		1,682,255		1,115,339
Americas Fabrication
Segment Reporting Information [Line Items]
Net sales	629,510	375,183	1,590,746	1,015,934
Adjusted EBITDA from continuing operations	(23,289)	(8,208)	(109,863)	(14,787)
Total assets	1,136,996		1,136,996		739,151
International Mill
Segment Reporting Information [Line Items]
Net sales	209,022	201,438	610,640	633,134
Adjusted EBITDA from continuing operations	24,120	31,987	77,436	95,066
Total assets	501,079		501,079		485,548
Corporate
Segment Reporting Information [Line Items]
Net sales	2,519	2,725	7,255	11,874
Adjusted EBITDA from continuing operations	(27,305)	(31,814)	(111,005)	(81,777)
Total assets	184,060		184,060		$ 696,428
Intersegment | Continuing Operations
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Intersegment | Americas Recycling
Segment Reporting Information [Line Items]
Net sales	60,229	71,419	183,244	171,618
Intersegment | Americas Mills
Segment Reporting Information [Line Items]
Net sales	330,868	220,604	860,964	550,573
Intersegment | Americas Fabrication
Segment Reporting Information [Line Items]
Net sales	3,537	3,058	10,248	8,059
Intersegment | International Mill
Segment Reporting Information [Line Items]
Net sales	343	299	947	846
Intersegment | Corporate
Segment Reporting Information [Line Items]
Net sales	(394,977)	(295,380)	(1,055,403)	(731,096)
Segments | Continuing Operations
Segment Reporting Information [Line Items]
Net sales	1,605,872	1,204,484	4,285,997	3,335,285
Segments | Americas Recycling
Segment Reporting Information [Line Items]
Net sales	289,015	364,098	878,099	1,004,066
Segments | Americas Mills
Segment Reporting Information [Line Items]
Net sales	866,903	553,063	2,243,465	1,392,468
Segments | Americas Fabrication
Segment Reporting Information [Line Items]
Net sales	633,047	378,241	1,600,994	1,023,993
Segments | International Mill
Segment Reporting Information [Line Items]
Net sales	209,365	201,737	611,587	633,980
Segments | Corporate
Segment Reporting Information [Line Items]
Net sales	$ (392,458)	$ (292,655)	$ (1,048,148)	$ (719,222)