Separation Transaction and Discontinued Operations - Summary of Discontinued Operations in Statement of Consolidated Cash Flows (Detail) - Alcoa Corporation - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation, depletion and amortization	$ 593	$ 772
Restructuring and other charges	102	981
Capital expenditures	$ 298	$ 391