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The cash inflow from sales of all investments, including securities and other assets, having ready marketability and intended by management to be liquidated, if necessary, beyond the current operating cycle.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Investments - Additional Information (Detail) - USD ($)		3 Months Ended	9 Months Ended
Investments - Additional Information (Detail) - USD ($)	Feb. 15, 2022	Mar. 31, 2022	Sep. 30, 2022	Sep. 30, 2021
ELYSIS TM Limited Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Basis in investment, due to share of losses			$ 0	$ 0
Unrecognized losses			$ 69,000,000
Brazil [Member] \| Mineracao Rio do Norte S.A [Member]
Schedule of Equity Method Investments [Line Items]
Proceeds from Sale of Long-term Investments	$ 10,000,000
Asset impairment charges		$ 58,000,000
Additional cash to be received upon satisfying post closing conditions	$ 30,000,000
Alcoa Corporation [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest in joint venture			25.10%
Maaden Alcoa Joint Venture [Member] \| Ma'aden [Member] \| SAUDI ARABIA
Schedule of Equity Method Investments [Line Items]
Ownership interest in joint venture			74.90%