OPERATING SEGMENTS (External Net Sales from Continuing Operations by Major Product) (Details) - USD ($) $ in Thousands	12 Months Ended
Aug. 31, 2021	Aug. 31, 2020	Aug. 31, 2019
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	$ 6,729,760	$ 5,476,486	$ 5,829,002
Segments \| North America
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	5,670,976	4,769,933	5,001,116
Segments \| Europe
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	1,049,059	699,140	817,048
Intersegment
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	0	0	0
Intersegment \| North America
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	0	0	0
Intersegment \| Europe
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	1,814	1,509	1,325
Corporate \| Segments
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	9,725	7,413	10,838
Corporate \| Intersegment
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	(1,814)	(1,509)	(1,325)
Unaffiliated Customers \| Segments
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	6,729,760	5,476,486	5,829,002
Unaffiliated Customers \| Segments \| North America
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	5,670,976	4,769,933	5,001,116
Unaffiliated Customers \| Segments \| Europe
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	1,047,245	697,631	815,723
Unaffiliated Customers \| Corporate \| Segments
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	11,539	8,922	12,163
Raw material products \| Segments
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	1,182,838	728,205	966,217
Raw material products \| Segments \| North America
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	1,162,997	718,513	953,858
Raw material products \| Segments \| Europe
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	19,841	9,692	12,359
Raw material products \| Corporate \| Segments
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	0	0	0
Steel products \| Segments
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	3,098,637	2,285,603	2,409,991
Steel products \| Segments \| North America
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	2,289,975	1,738,556	1,763,017
Steel products \| Segments \| Europe
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	808,662	547,047	646,974
Steel products \| Corporate \| Segments
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	0	0	0
Downstream products \| Segments
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	2,006,367	2,062,358	2,070,817
Downstream products \| Segments \| North America
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	1,814,192	1,943,126	1,936,994
Downstream products \| Segments \| Europe
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	192,175	119,232	133,823
Downstream products \| Corporate \| Segments
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	0	0	0
Other \| Segments
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	441,918	400,320	381,977
Other \| Segments \| North America
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	403,812	369,738	347,247
Other \| Segments \| Europe
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	26,567	21,660	22,567
Other \| Corporate \| Segments
Entity-Wide Information, Revenue from External Customer [Line Items]
Net sales	$ 11,539	$ 8,922	$ 12,163