BUSINESS SEGMENTS (Summary of Certain Financial Information from Continuing Operations by Reportable Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 28, 2019	Feb. 28, 2018	Feb. 28, 2019	Feb. 28, 2018	Aug. 31, 2018
Segment Reporting Information [Line Items]
Net sales	$ 1,402,783	$ 1,054,268	$ 2,680,125	$ 2,130,801
Adjusted EBITDA from continuing operations	69,333	64,876	134,869	144,143
Total assets	3,728,692		3,728,692		$ 3,328,304
Continuing Operations
Segment Reporting Information [Line Items]
Net sales	1,402,783	1,054,268	2,680,125	2,130,801
Adjusted EBITDA from continuing operations	69,333	64,876	134,869	144,143
Total assets	3,728,692		3,728,692		3,328,304
Americas Recycling
Segment Reporting Information [Line Items]
Net sales	225,888	265,432	466,069	539,769
Adjusted EBITDA from continuing operations	10,124	17,216	25,558	32,221
Total assets	275,106		275,106		291,838
Americas Mills
Segment Reporting Information [Line Items]
Net sales	472,795	262,703	846,466	509,436
Adjusted EBITDA from continuing operations	112,396	50,219	226,269	105,385
Total assets	1,730,523		1,730,523		1,115,339
Americas Fabrication
Segment Reporting Information [Line Items]
Net sales	526,678	310,199	961,236	640,751
Adjusted EBITDA from continuing operations	(49,578)	(8,611)	(86,574)	(6,579)
Total assets	1,085,078		1,085,078		739,151
International Mill
Segment Reporting Information [Line Items]
Net sales	174,945	211,484	401,618	431,696
Adjusted EBITDA from continuing operations	20,537	32,135	53,316	63,079
Total assets	507,775		507,775		485,548
Corporate
Segment Reporting Information [Line Items]
Net sales	2,477	4,450	4,736	9,149
Adjusted EBITDA from continuing operations	(24,146)	(26,083)	(83,700)	(49,963)
Total assets	130,210		130,210		$ 696,428
Segments | Continuing Operations
Segment Reporting Information [Line Items]
Net sales	1,402,783	1,054,268	2,680,125	2,130,801
Segments | Americas Recycling
Segment Reporting Information [Line Items]
Net sales	287,075	320,627	589,084	639,968
Segments | Americas Mills
Segment Reporting Information [Line Items]
Net sales	774,709	425,887	1,376,562	839,405
Segments | Americas Fabrication
Segment Reporting Information [Line Items]
Net sales	530,836	312,973	967,947	645,752
Segments | International Mill
Segment Reporting Information [Line Items]
Net sales	175,198	211,765	402,222	432,242
Segments | Corporate
Segment Reporting Information [Line Items]
Net sales	(365,035)	(216,984)	(655,690)	(426,566)
Intersegment | Continuing Operations
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Intersegment | Americas Recycling
Segment Reporting Information [Line Items]
Net sales	61,187	55,195	123,015	100,199
Intersegment | Americas Mills
Segment Reporting Information [Line Items]
Net sales	301,914	163,184	530,096	329,969
Intersegment | Americas Fabrication
Segment Reporting Information [Line Items]
Net sales	4,158	2,774	6,711	5,001
Intersegment | International Mill
Segment Reporting Information [Line Items]
Net sales	253	281	604	546
Intersegment | Corporate
Segment Reporting Information [Line Items]
Net sales	$ (367,512)	$ (221,434)	$ (660,426)	$ (435,715)