Segment Information - Segment Revenue Reconciliation to Consolidated (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 28, 2019	Feb. 28, 2018	Feb. 28, 2019	Feb. 28, 2018
Segment Reporting Information [Line Items]
Revenues	$ 473,565	$ 559,443	$ 1,037,585	$ 1,042,722
Auto and Metals Recycling
Segment Reporting Information [Line Items]
Revenues	386,065		822,477
Cascade Steel and Scrap
Segment Reporting Information [Line Items]
Revenues	90,398		220,784
Operating Segments | Auto and Metals Recycling
Segment Reporting Information [Line Items]
Revenues	386,065	449,785	822,477	847,839
Operating Segments | Cascade Steel and Scrap
Segment Reporting Information [Line Items]
Revenues	90,398	116,714	220,784	206,698
Less: Intersegment revenues | Auto and Metals Recycling
Segment Reporting Information [Line Items]
Revenues	(2,898)	(7,056)	(5,676)	(11,815)
Segment Reconciling Items | Auto and Metals Recycling
Segment Reporting Information [Line Items]
Revenues	$ 383,167	$ 442,729	$ 816,801	$ 836,024