Commitments and Contingencies - Recycling Operations and Other Legacy (Details)			1 Months Ended	3 Months Ended	6 Months Ended
	Dec. 31, 2017 potentially_responsible_party	Aug. 31, 2007 USD ($)	Jan. 31, 2017 USD ($)	Nov. 30, 2017 USD ($)	Feb. 28, 2019 USD ($)	Aug. 31, 2018 USD ($)	Jan. 30, 2017 potentially_responsible_party party	Aug. 31, 2016 USD ($)
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies					$ 53,214,000	$ 53,832,000
Parties Liable in Litigation | party							30
Liabilities Established					1,487,000
Insurance Receivable					15,000,000	36,000,000
Legacy Environmental Site 1 - Remediation of Shredder Residue
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies					4,000,000	4,000,000
Environmental remediation expense accrued in the period				$ 4,000,000
Legacy Environmental Site 2 - Remediation of Soil and Groundwater Conditions
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies					8,000,000	6,000,000
Portland Harbor Superfund Site
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies					1,000,000	2,000,000
Number Of Potentially Responsible Parties Joining Allocation Process | potentially_responsible_party							100
Number Of Other Potentially Responsible Parties Signing Settlement Agreement and Order on Consent | potentially_responsible_party	3
Number of Years for Pre-Remedial Design	2 years
Liabilities Established				2,000,000
Insurance Receivable				$ 2,000,000
Other Auto and Metals Recycling Business Sites
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies					53,000,000	$ 54,000,000
Minimum | Legacy Environmental Site 1 - Remediation of Shredder Residue
Loss Contingencies [Line Items]
Loss contingency, range of possible loss					0
Maximum | Legacy Environmental Site 1 - Remediation of Shredder Residue
Loss Contingencies [Line Items]
Loss contingency, range of possible loss					$ 28,000,000
Lower Willamette Group | Portland Harbor Superfund Site
Loss Contingencies [Line Items]
Remedial Investigation and Feasibility Study Costs		$ 115,000,000
Number of Years for Remedial Investigation and Feasibility Study		10 years
Potential Responsible Parties | Portland Harbor Superfund Site
Loss Contingencies [Line Items]
Estimated Cost of Selected Remedy Undiscounted			$ 1,700,000,000
Estimated Cost of Selected Remedy Discounted			$ 1,050,000,000.00
Estimated Cost of Selected Remedy, Discount Rate			7.00%
Site Contingency, Estimated Construction Time Frame			13 years
Potential Responsible Parties | Minimum | Portland Harbor Superfund Site
Loss Contingencies [Line Items]
Site Contingency, Least Costly Remediation Plan Discounted								$ 170,000,000
Estimated Cost of Selected Remedy, Range			(30.00%)
Potential Responsible Parties | Maximum | Portland Harbor Superfund Site
Loss Contingencies [Line Items]
Site Contingency, Most Costly Remediation Plan Discounted								$ 2,500,000,000
Estimated Cost of Selected Remedy, Range			50.00%