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BUSINESS SEGMENTS (External Net Sales from Continuing Operations by Major Product) (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Aug. 31, 2018 | [1] | May 31, 2018 | [1] | Feb. 28, 2018 | [1] | Nov. 30, 2017 | [1] | Aug. 31, 2017 | May 31, 2017 | [1] | Feb. 28, 2017 | [1] | Nov. 30, 2016 | [1] | Aug. 31, 2018 | Aug. 31, 2017 | Aug. 31, 2016
Entity-Wide Information, Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net sales | $ 1,308,438 | $ 1,204,484 | $ 1,054,268 | $ 1,076,533 | $ 1,084,130 | $ 1,044,713 | $ 862,298 | $ 852,928 | $ 4,643,723 | $ 3,844,069 | $ 3,596,068
Steel products |  |  |  |  |  |  |  |  |  |  |
Entity-Wide Information, Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net sales |  |  |  |  |  |  |  |  | 3,114,227 | 2,584,359 | 2,620,452
Nonferrous scrap |  |  |  |  |  |  |  |  |  |  |
Entity-Wide Information, Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net sales |  |  |  |  |  |  |  |  | 630,609 | 506,220 | 364,690
Ferrous scrap |  |  |  |  |  |  |  |  |  |  |
Entity-Wide Information, Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net sales |  |  |  |  |  |  |  |  | 550,602 | 413,441 | 266,326
Construction materials |  |  |  |  |  |  |  |  |  |  |
Entity-Wide Information, Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net sales |  |  |  |  |  |  |  |  | 249,538 | 228,910 | 234,513
Other |  |  |  |  |  |  |  |  |  |  |
Entity-Wide Information, Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net sales |  |  |  |  |  |  |  |  | $ 98,747 | $ 111,139 | $ 110,087
[1] | Excludes discontinued operations. See Note 3, Changes in Business

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