Segment Information - Schedule of Revenues from External Customers By Major Product and Destination (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Aug. 31, 2019	May 31, 2019	Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2019	Aug. 31, 2018	Aug. 31, 2017
Segment Reporting Information [Line Items]
Revenues	$ 547,800	$ 547,396	$ 473,565	$ 564,020	$ 669,577	$ 652,416	$ 559,443	$ 483,279	$ 2,132,781	$ 2,364,715	$ 1,687,591
Ferrous revenues
Segment Reporting Information [Line Items]
Revenues									1,164,719	1,328,447	855,161
Nonferrous revenues
Segment Reporting Information [Line Items]
Revenues									468,023	529,466	425,989
Steel Revenues
Segment Reporting Information [Line Items]
Revenues									367,956	367,560	280,767
Retail and other revenues
Segment Reporting Information [Line Items]
Revenues									132,083	139,242	125,674
Foreign
Segment Reporting Information [Line Items]
Revenues									1,141,077	1,354,460	894,265
Domestic
Segment Reporting Information [Line Items]
Revenues									$ 991,704	$ 1,010,255	$ 793,326