Derivatives, Hedging Programs and Other Financial Instruments - Summary of Derivative Positions (Details) mmlb in Millions	3 Months Ended
	Mar. 31, 2022 EUR (€) mmlb MMBTU MWh
Purchase | Aluminum
Derivative [Line Items]
Derivative non-monetary notional amount	109.3
Purchase | Aluminum | Minimum
Derivative [Line Items]
Derivative maturity period	2022-04
Purchase | Aluminum | Maximum
Derivative [Line Items]
Derivative maturity period	2023-12
Purchase | Midwest premium swap contracts
Derivative [Line Items]
Derivative non-monetary notional amount	92.0
Purchase | Midwest premium swap contracts | Minimum
Derivative [Line Items]
Derivative maturity period	2022-04
Purchase | Midwest premium swap contracts | Maximum
Derivative [Line Items]
Derivative maturity period	2023-12
Purchase | Alloying Metals
Derivative [Line Items]
Derivative non-monetary notional amount	4.8
Purchase | Alloying Metals | Minimum
Derivative [Line Items]
Derivative maturity period	2022-04
Purchase | Alloying Metals | Maximum
Derivative [Line Items]
Derivative maturity period	2022-12
Purchase | Natural Gas
Derivative [Line Items]
Derivative non-monetary notional amount | MMBTU	4,740,000
Purchase | Natural Gas | Minimum
Derivative [Line Items]
Derivative maturity period	2022-04
Purchase | Natural Gas | Maximum
Derivative [Line Items]
Derivative maturity period	2025-12
Purchase | Foreign Exchange Contract
Derivative [Line Items]
Derivative notional amount | €	€ 138,720
Purchase | Foreign Exchange Contract | Minimum
Derivative [Line Items]
Derivative maturity period	2022-06
Purchase | Foreign Exchange Contract | Maximum
Derivative [Line Items]
Derivative maturity period	2023-03
Purchase | Electricity
Derivative [Line Items]
Derivative non-monetary notional amount | MWh	165,025
Purchase | Electricity | Minimum
Derivative [Line Items]
Derivative maturity period	2022-04
Purchase | Electricity | Maximum
Derivative [Line Items]
Derivative maturity period	2022-12
Sales | Aluminum
Derivative [Line Items]
Derivative non-monetary notional amount	3.0
Sales | Aluminum | Minimum
Derivative [Line Items]
Derivative maturity period	2022-08
Sales | Aluminum | Maximum
Derivative [Line Items]
Derivative maturity period	2022-10