v3.23.2

Fair Value Measures and Disclosures (Details) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2023 USD ($) MMBTU kiloMetricTon MWh	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Jun. 30, 2023 USD ($) MMBTU kiloMetricTon MWh	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($) MMBTU kiloMetricTon
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	$ 53				$ 53		$ 21
Derivative Liability	14				14		8
Unrealized Gain (Loss) on Cash Flow Hedging Instruments	55	$ 201			34	$ 58
Realized Gain (Loss) on Cash Flow Hedging Instruments	11	(46)			5	(99)
Unrealized Gain (Loss) on Derivatives	18	21			(2)	23
Designated as Hedging Instrument | Aluminum Contract | Cash Flow Hedging
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	48				48		0
Derivative Liability	0				0		$ (14)
Designated as Hedging Instrument | Aluminum Contract | Cash Flow Hedging | Other Comprehensive Income (Loss)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unrealized Gain (Loss) on Cash Flow Hedging Instruments	$ 58	203			$ 49	47
Designated as Hedging Instrument | Aluminum Contract | Cash Flow Hedging | Other Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative, Nonmonetary Notional Amount	242				242		17
Designated as Hedging Instrument | Aluminum Contract | Cash Flow Hedging | Other Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative, Nonmonetary Notional Amount | kiloMetricTon	29				29		368
Designated as Hedging Instrument | Aluminum Contract | Cash Flow Hedging | Sales
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Realized Gain (Loss) on Cash Flow Hedging Instruments	$ 18	(53)			$ 17	(107)
Designated as Hedging Instrument | Aluminum Contract | Cash Flow Hedging | Cost of Sales
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Realized Gain (Loss) on Cash Flow Hedging Instruments	0	0			0	(1)
Designated as Hedging Instrument | Commodity Contract | Cash Flow Hedging
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	(1)				(1)		$ (1)
Derivative Liability	1				1		$ 1
Designated as Hedging Instrument | Commodity Contract | Cash Flow Hedging | Other Comprehensive Income (Loss)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unrealized Gain (Loss) on Cash Flow Hedging Instruments	$ (2)	(2)			$ (1)	(2)
Designated as Hedging Instrument | Commodity Contract | Cash Flow Hedging | Other Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative, Nonmonetary Notional Amount | kiloMetricTon	1				1		1
Designated as Hedging Instrument | Commodity Contract | Cash Flow Hedging | Other Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative, Nonmonetary Notional Amount | kiloMetricTon	6				6		3
Designated as Hedging Instrument | Commodity Contract | Cash Flow Hedging | Cost of Sales
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Realized Gain (Loss) on Cash Flow Hedging Instruments	$ 1	0			$ 1	0
Designated as Hedging Instrument | Energy Related Derivative | Cash Flow Hedging
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	9				9		$ 5
Designated as Hedging Instrument | Energy Related Derivative | Cash Flow Hedging | Other Comprehensive Income (Loss)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unrealized Gain (Loss) on Cash Flow Hedging Instruments	$ (1)	0			$ (14)	13
Designated as Hedging Instrument | Energy Related Derivative | Cash Flow Hedging | Other Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU	7.5				7.5		6.3
Designated as Hedging Instrument | Energy Related Derivative | Cash Flow Hedging | Cost of Sales
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Realized Gain (Loss) on Cash Flow Hedging Instruments	$ 6	(7)			$ 11	(7)
Not Designated as Hedging Instrument
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unrealized Gain (Loss) on Derivatives	18	24			(2)	29
Realized Gain (Loss) on Derivatives	(14)	4			(11)	2
Not Designated as Hedging Instrument | Aluminum Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	9				9		$ 6
Derivative Liability	$ 2				$ 2		$ 12
Not Designated as Hedging Instrument | Aluminum Contract | Other Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative, Nonmonetary Notional Amount | kiloMetricTon	33				33		60
Not Designated as Hedging Instrument | Aluminum Contract | Other Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative, Nonmonetary Notional Amount | kiloMetricTon	1				1		53
Not Designated as Hedging Instrument | Aluminum Contract | Sales
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unrealized Gain (Loss) on Derivatives	$ 19	4			$ 14	6
Realized Gain (Loss) on Derivatives	(10)	4			(6)	2
Not Designated as Hedging Instrument | Energy Related Derivative
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	(3)				(3)		$ 16
Derivative Liability	$ 2				$ 2		$ 4
Not Designated as Hedging Instrument | Energy Related Derivative | Other Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU	4.7				4.7		12.1
Not Designated as Hedging Instrument | Energy Related Derivative | Other Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU	2.7				2.7		0.6
Not Designated as Hedging Instrument | Energy Related Derivative | Cost of Sales
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unrealized Gain (Loss) on Derivatives	$ 1	(20)			$ 16	(23)
Realized Gain (Loss) on Derivatives	4	0			5	0
Not Designated as Hedging Instrument | Natural Gas Contract | Cost of Sales
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unrealized Gain (Loss) on Derivatives			$ 6	$ 2		$ (5)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		$ 3
Not Designated as Hedging Instrument | Electricity Derivative
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	$ 0				$ 0		$ 0
Not Designated as Hedging Instrument | Electricity Derivative | Other Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative, Nonmonetary Notional Amount | MWh	8,314				8,314
Reported Value Measurement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	$ 266				$ 266		261
Derivative Asset	53				53		21
Derivative Liability	14				14		8
Debt, fair value	1,598				1,598		1,597
Estimate of Fair Value Measurement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	266				266		261
Derivative Asset	53				53		21
Derivative Liability	14				14		8
Debt, fair value	$ 1,620				$ 1,620		$ 1,539

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