Derivatives, Hedging Programs and Other Financial Instruments - Summary of Derivative Positions (Details) Mmlb in Millions	6 Months Ended
	Jun. 30, 2023 Mmlb GBP (£) MMBTU EUR (€)
Purchase | Euro
Derivative [Line Items]
Derivative non-monetary notional amount | €	5,857,416
Purchase | British Pounds
Derivative [Line Items]
Derivative non-monetary notional amount | £	77,742
Purchase | Minimum | Euro
Derivative [Line Items]
Derivative maturity period	Jul. 31, 2023
Purchase | Minimum | British Pounds
Derivative [Line Items]
Derivative maturity period	Aug. 31, 2023
Purchase | Maximum | Euro
Derivative [Line Items]
Derivative maturity period	Jun. 30, 2024
Purchase | Maximum | British Pounds
Derivative [Line Items]
Derivative maturity period	Sep. 30, 2023
Purchase | Natural Gas
Derivative [Line Items]
Derivative non-monetary notional amount | MMBTU	3,360,000
Purchase | Natural Gas | Minimum
Derivative [Line Items]
Derivative maturity period	Jul. 31, 2023
Purchase | Natural Gas | Maximum
Derivative [Line Items]
Derivative maturity period	Dec. 31, 2026
Purchase | Aluminum
Derivative [Line Items]
Derivative non-monetary notional amount	91.9
Purchase | Aluminum | Minimum
Derivative [Line Items]
Derivative maturity period	Jul. 31, 2023
Purchase | Aluminum | Maximum
Derivative [Line Items]
Derivative maturity period	Oct. 31, 2024
Purchase | Midwest premium purchase contracts
Derivative [Line Items]
Derivative non-monetary notional amount	82.8
Purchase | Midwest premium purchase contracts | Minimum
Derivative [Line Items]
Derivative maturity period	Jul. 31, 2023
Purchase | Midwest premium purchase contracts | Maximum
Derivative [Line Items]
Derivative maturity period	Oct. 31, 2024
Purchase | Alloying Metals
Derivative [Line Items]
Derivative non-monetary notional amount	1.7
Purchase | Alloying Metals | Minimum
Derivative [Line Items]
Derivative maturity period	Jul. 31, 2023
Purchase | Alloying Metals | Maximum
Derivative [Line Items]
Derivative maturity period	Dec. 31, 2024
Sales | British Pounds
Derivative [Line Items]
Derivative non-monetary notional amount | £	77,742
Sales | Minimum | British Pounds
Derivative [Line Items]
Derivative maturity period	Aug. 31, 2023
Sales | Maximum | British Pounds
Derivative [Line Items]
Derivative maturity period	Sep. 30, 2023
Sales | Aluminum
Derivative [Line Items]
Derivative non-monetary notional amount	21.6
Sales | Aluminum | Minimum
Derivative [Line Items]
Derivative maturity period	Jul. 31, 2023
Sales | Aluminum | Maximum
Derivative [Line Items]
Derivative maturity period	Oct. 31, 2023
Sales | Midwest premium sale contracts
Derivative [Line Items]
Derivative non-monetary notional amount	41.9
Sales | Midwest premium sale contracts | Minimum
Derivative [Line Items]
Derivative maturity period	Jul. 31, 2023
Sales | Midwest premium sale contracts | Maximum
Derivative [Line Items]
Derivative maturity period	Oct. 31, 2023