Summary of Significant Accounting Policies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) pot_line	Dec. 31, 2018 USD ($)
Schedule of Equity Method Investments [Line Items]
Glencore beneficial ownership	42.90%
Glencore economic ownership	46.90%
Allowance for doubtful accounts receivable | $	$ 1,000	$ 1,000
Property, Plant and Equipment [Line Items]
Number of potlines rebuilt | pot_line	2
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