Separation Transaction and Discontinued Operations - Summary of Discontinued Operations in Statement of Consolidated Operations (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income from discontinued operations after income taxes	$ 125	$ 26
Less: Net income from discontinued operations attributable to noncontrolling interests	43	38
Net income (loss) from discontinued operations	82	(12)
Alcoa Corporation [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales	2,061	3,953
Cost of goods sold (exclusive of expenses below)	1,683	3,324
Selling, general administrative, and other expenses	47	102
Research and development expenses	7	18
Provision for depreciation, depletion and amortization	177	352
Restructuring and other charges	9	86
Interest expense	5	11
Other (income) expense, net	(21)	26
Income from discontinued operations before income taxes	154	34
Provision for income taxes	29	8
Income from discontinued operations after income taxes	125	26
Less: Net income from discontinued operations attributable to noncontrolling interests	43	38
Net income (loss) from discontinued operations	$ 82	$ (12)