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v3.20.4

Summary of Significant Accounting Policies (Details) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 USD ($) pot_line | Dec. 31, 2019 USD ($)
Schedule of Equity Method Investments [Line Items] |  |
Allowance for expected losses | $ | $ 1.0 | $ 1.0
Property, Plant and Equipment [Line Items] |  |
Number of potlines rebuilt | pot_line | 2 |
Glencore [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Glencore beneficial ownership | 42.90% |
Glencore economic ownership | 46.80% |
Minimum [Member] | Building and Improvements [Member] |  |
Property, Plant and Equipment [Line Items] |  |
Useful life | 10 years |
Minimum [Member] | Machinery and Equipment [Member] |  |
Property, Plant and Equipment [Line Items] |  |
Useful life | 5 years |
Minimum [Member] | Technology and Software [Member] |  |
Property, Plant and Equipment [Line Items] |  |
Useful life | 3 years |
Maximum [Member] | Building and Improvements [Member] |  |
Property, Plant and Equipment [Line Items] |  |
Useful life | 45 years |
Maximum [Member] | Machinery and Equipment [Member] |  |
Property, Plant and Equipment [Line Items] |  |
Useful life | 35 years |
Maximum [Member] | Technology and Software [Member] |  |
Property, Plant and Equipment [Line Items] |  |
Useful life | 7 years |

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