Business, Product and Geographical Area Information and Concentration of Risk - Schedule of Export Sales and Primary Aluminum Supply from Major Suppliers (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Export Sales | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage	10.00%	14.00%	15.00%
Aluminum | Supplier Concentration Risk | Top Five Major Suppliers
Concentration Risk [Line Items]
Concentration risk, percentage	72.00%	74.00%	81.00%
Aluminum | Supplier Concentration Risk | Largest Supplier
Concentration Risk [Line Items]
Concentration risk, percentage	21.00%	22.00%	22.00%
Aluminum | Supplier Concentration Risk | Second and Third Largest Suppliers
Concentration Risk [Line Items]
Concentration risk, percentage	32.00%	32.00%	38.00%