Separation Transaction and Discontinued Operations - Summary of Discontinued Operations in Statement of Consolidated Operations (Detail) - USD ($) $ in Millions	10 Months Ended	12 Months Ended
	Oct. 31, 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]
Income (loss) from discontinued operations after income taxes		$ 184	$ (41)	$ 238
Less: Net income (loss) from discontinued operations attributable to noncontrolling interests		63	124	(91)
Net income (loss) from discontinued operations		$ 121	165	(329)
Alcoa Corporation [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales	$ 6,752		10,121	11,364
Cost of goods sold (exclusive of expenses below)	5,655		7,965	8,782
Selling, general administrative, and other expenses	164		214	231
Research and development	28		69	95
Provision for depreciation, depletion and amortization	593		772	935
Restructuring and other charges	102		981	854
Interest expense	28		25	31
Other (income) expenses, net	(75)		30	52
Income from discontinued operations before income taxes	257		65	384
Provision for income taxes	73		106	146
Income (loss) from discontinued operations after income taxes	184		(41)	238
Less: Net income (loss) from discontinued operations attributable to noncontrolling interests	63		124	(91)
Net income (loss) from discontinued operations	$ 121		$ (165)	$ 329