BUSINESS SEGMENTS (Summary of Certain Financial Information from Continuing Operations by Reportable Segment and Major Product) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		9 Months Ended
	Feb. 28, 2022	Feb. 28, 2021	Feb. 28, 2022	Feb. 28, 2021	May 31, 2021	Aug. 31, 2021
Segment Reporting Information [Line Items]
Net sales	$ 2,008,888	$ 1,462,270	$ 3,990,689	$ 2,854,073
Adjusted EBITDA from continuing operations	564,119	141,733	878,141	285,366
Total assets	5,504,220		5,504,220			$ 4,638,671
Segments | Continuing Operations
Segment Reporting Information [Line Items]
Net sales	2,008,888	1,462,270	3,990,689	2,854,073
Adjusted EBITDA from continuing operations	564,119	141,733	878,141		$ 285,366
Total assets	5,504,220		5,504,220			4,638,671
Segments | North America
Segment Reporting Information [Line Items]
Net sales	1,614,224	1,257,486	3,267,846	2,452,499
Adjusted EBITDA from continuing operations	535,463	171,612	803,987		327,246
Total assets	3,553,719		3,553,719			3,221,465
Segments | Europe
Segment Reporting Information [Line Items]
Net sales	395,758	202,066	724,814	396,662
Adjusted EBITDA from continuing operations	81,149	16,107	160,981		30,577
Total assets	823,127		823,127			729,766
Segments | Unaffiliated Customers
Segment Reporting Information [Line Items]
Net sales	2,008,888	1,462,270	3,990,689	2,854,073
Segments | Unaffiliated Customers | North America
Segment Reporting Information [Line Items]
Net sales	1,614,224	1,257,486	3,267,846	2,452,499
Segments | Unaffiliated Customers | Europe
Segment Reporting Information [Line Items]
Net sales	395,349	201,559	723,911	395,744
Segments | Raw materials
Segment Reporting Information [Line Items]
Net sales	372,805	259,787	732,857	472,854
Segments | Raw materials | North America
Segment Reporting Information [Line Items]
Net sales	366,941	255,012	720,033	465,249
Segments | Raw materials | Europe
Segment Reporting Information [Line Items]
Net sales	5,864	4,775	12,824	7,605
Segments | Steel Products
Segment Reporting Information [Line Items]
Net sales	986,461	671,683	1,904,648	1,280,795
Segments | Steel Products | North America
Segment Reporting Information [Line Items]
Net sales	666,047	514,201	1,341,089	971,858
Segments | Steel Products | Europe
Segment Reporting Information [Line Items]
Net sales	320,414	157,482	563,559	308,937
Segments | Downstream products
Segment Reporting Information [Line Items]
Net sales	519,294	434,159	1,103,762	905,661
Segments | Downstream products | North America
Segment Reporting Information [Line Items]
Net sales	459,753	400,397	974,149	837,426
Segments | Downstream products | Europe
Segment Reporting Information [Line Items]
Net sales	59,541	33,762	129,613	68,235
Segments | Other
Segment Reporting Information [Line Items]
Net sales	130,328	96,641	249,422	194,763
Segments | Other | North America
Segment Reporting Information [Line Items]
Net sales	121,483	87,876	232,575	177,966
Segments | Other | Europe
Segment Reporting Information [Line Items]
Net sales	9,530	5,540	17,915	10,967
Segments | Corporate
Segment Reporting Information [Line Items]
Net sales	(1,094)	2,718	(1,971)
Adjusted EBITDA from continuing operations	(52,493)	(45,986)
Segments | Corporate | Unaffiliated Customers
Segment Reporting Information [Line Items]
Net sales	(685)	3,225	(1,068)	5,830
Segments | Corporate | Raw materials
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Segments | Corporate | Steel Products
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Segments | Corporate | Downstream products
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Segments | Corporate | Other
Segment Reporting Information [Line Items]
Net sales	(685)	3,225	(1,068)	5,830
Segments | Corporate and Other
Segment Reporting Information [Line Items]
Net sales				4,912
Adjusted EBITDA from continuing operations			(86,827)		$ (72,457)
Total assets	1,127,374		1,127,374			$ 687,440
Intersegment
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Intersegment | North America
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Intersegment | Europe
Segment Reporting Information [Line Items]
Net sales	409	507	903	918
Intersegment | Corporate
Segment Reporting Information [Line Items]
Net sales	$ (409)	$ (507)	$ (903)	$ (918)