Segment Information - Summary of Total Assets (Details) - USD ($) $ in Thousands	Aug. 31, 2019	Aug. 31, 2018
Segment Reporting Information [Line Items]
Total assets	$ 1,160,746	$ 1,104,817
Property, plant and equipment, net	456,400	415,711
Operating Segments
Segment Reporting Information [Line Items]
Total assets	2,331,197	2,226,593
Operating Segments | Auto and Metals Recycling
Segment Reporting Information [Line Items]
Total assets	1,561,267	1,485,626
Operating Segments | Cascade Steel and Scrap
Segment Reporting Information [Line Items]
Total assets	769,930	740,967
Corporate and eliminations
Segment Reporting Information [Line Items]
Total assets	$ (1,170,451)	$ (1,121,776)