Separation Transaction and Discontinued Operations - Summary of Discontinued Operations in Statement of Consolidated Operations (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from discontinued operations after income taxes	$ (99)
Less: Net loss from discontinued operations attributable to noncontrolling interests	(5)
Net loss from discontinued operations	(94)
Alcoa Corporation [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales	1,892
Cost of goods sold (exclusive of expenses below)	1,641
Selling, general administrative, and other expenses	55
Research and development expenses	11
Provision for depreciation, depletion and amortization	175
Restructuring and other charges	77
Interest expense	6
Other expenses, net	47
Loss from discontinued operations before income taxes	(120)
Benefit for income taxes	(21)
Loss from discontinued operations after income taxes	(99)
Less: Net loss from discontinued operations attributable to noncontrolling interests	(5)
Net loss from discontinued operations	$ (94)