Segment Information - Segment Assets Reconciliation to Consolidated (Details) - USD ($) $ in Thousands	Feb. 28, 2019	Aug. 31, 2018
Segment Reporting Information [Line Items]
Investments in joint ventures	$ 10,703	$ 11,532
Assets	1,087,252	1,104,817
Auto and Metals Recycling
Segment Reporting Information [Line Items]
Investments in joint ventures	3,000	4,000
Cascade Steel and Scrap
Segment Reporting Information [Line Items]
Investments in joint ventures	8,000	8,000
Operating Segments
Segment Reporting Information [Line Items]
Assets	2,249,815	2,226,593
Operating Segments | Auto and Metals Recycling
Segment Reporting Information [Line Items]
Assets	1,497,819	1,485,626
Operating Segments | Cascade Steel and Scrap
Segment Reporting Information [Line Items]
Assets	751,996	740,967
Corporate and eliminations
Segment Reporting Information [Line Items]
Assets	$ (1,162,563)	$ (1,121,776)