Separation Transaction and Discontinued Operations - Additional Information (Detail) - USD ($)		12 Months Ended
	Nov. 01, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Receivable under separation and distribution agreement included in other receivables		$ 243,000,000
Debt issuance and capital expenditures incurred		110,000,000
Impairment charges	$ 0	80,000,000		$ 65,000,000
Selling, General Administrative, and Other Expenses [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Costs related to separation transaction, pre-tax		193,000,000	$ 24,000,000
Costs related to separation transaction, after-tax		$ 158,000,000	$ 24,000,000
Alcoa Corporation [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Common stock outstanding percentage	80.10%
Percentage of common stock retained		19.90%
Common stock conversion ratio		0.333
Number of common stock retained		36,311,767