Financial Instruments and Risk Management - General (Details) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($) approach $ / shares shares	Dec. 31, 2020 USD ($)
Financial Instruments and Risk Management
Aggregate fair value of derivative instruments with credit-risk-related contingent features that were in a net liability position	$ 15	$ 52
Collateral amount posted for derivative instruments with credit-risk-related contingent features that were in a net liability position	$ 0	$ 0
Commodity contracts
Financial Instruments and Risk Management
Number of methods through which entity manages commodity price risk in connection with market price fluctuations of aluminum ingot | approach	2
Notional amount of derivatives	$ 1,375
Gain (loss) on derivatives included in AOCI, net of tax	80
Net gain (loss) expected to be recognized in the consolidated statement of earnings during the next 12 months	$ 66
Period within which derivative will expire	3 years
Interest rate swap and option contracts
Financial Instruments and Risk Management
Notional amount of derivatives	$ 1,171
Period within which derivative will expire	1 year
Currency Exchange Rate Risk
Financial Instruments and Risk Management
Notional amount of derivatives	$ 2,724
Gain (loss) on derivatives included in AOCI, net of tax	24
Net gain (loss) expected to be recognized in the consolidated statement of earnings during the next 12 months	$ 17
Period within which derivative will expire	4 years
Equity contracts
Financial Instruments and Risk Management
Combined notional value (in shares) | shares	2.6
Change in company's stock price (in dollars per share) | $ / shares	$ 1