Preferred and Common Stock - Additional Information (Detail) - USD ($)			2 Months Ended	12 Months Ended
	Feb. 14, 2017	Nov. 01, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Oct. 31, 2016
Class of Stock [Line Items]
Preferred stock, authorized (in shares)			100,000,000	100,000,000
Preferred stock, par value (in dollars per share)			$ 0.01	$ 0.01
Preferred stock, issued (in shares)			0	0
Common stock shares authorized			750,000,000	750,000,000
Common stock par value		$ 0.01	$ 0.01	$ 0.01
Common stock shares issued		182,471,195	182,930,995	182,930,995			0
Common stock distributed related to separation transaction		146,159,428
Common stock shares retained by ParentCo		36,311,767
Common stock share outstanding			182,930,995	182,930,995			0
Common stock dividends declared during period			$ 0
Common stock were reserved for future issuance			18,540,200	18,540,200
Increase in exercise price		$ 1.34
Adjusted exercise option price		$ 28.72	$ 21.44	$ 21.44
Stock based compensation expense				$ 28,000,000	$ 35,000,000	$ 39,000,000
Stock based compensation expense, stock awards percentage				80.00%	80.00%	80.00%
Expense related to the acceleration of expense related to retirement-eligible employees				$ 7,000,000	$ 6,000,000	$ 8,000,000
Fair value of stock options granted				$ 2.12	$ 4.47	$ 2.84
Average risk-free interest rate				2.06%
Dividend yield				1.10%
Volatility				44.50%
Annual pre- and post-vesting forfeitures				7.00%
Exercise behavior				60.00%
Life (years)				5 years 8 months 12 days
Description of reverse stock split				ParentCo's stock-based compensation plan to Alcoa Corporation employees, the previously-mentioned fair values were adjusted to reflect both the impact of ParentCo's 1-for-3 reverse stock split that occurred on October 5, 2016 and to maintain the intrinsic value of the stock options as a result of the Separation Transaction
Number of options, Outstanding weighted average remaining contractual life				5 years 8 months 27 days
Total intrinsic value of options outstanding			$ 21,000,000	$ 21,000,000
Stock options vested				2,786,416
Stock option exercisable				2,786,416
Weighted average remaining contractual life, vested and exercisable				4 years 5 months 9 days
Weighted average exercise price, vested and exercisable			$ 26.92	$ 26.92
Total intrinsic value of options vested and exercisable			$ 9,000,000	$ 9,000,000
Cash received from option exercises				10,000,000
Total intrinsic value of options exercised				4,000,000
Unrecognized compensation costs on non-vested stock option grants (pretax)			$ 17,000,000	$ 17,000,000
Unrecognized compensation costs on non-vested awards, weighted average period of recognition in years				1 year 6 months
Common Stock [Member]
Class of Stock [Line Items]
Shares issued for employee stock-based compensation plans			459,800
Alcoa Corporation [Member]
Class of Stock [Line Items]
Fair value of stock options granted				$ 4.75	$ 10.01	$ 6.36
Employees [Member]
Class of Stock [Line Items]
Stock based compensation expense				$ 16,000,000	$ 21,000,000	$ 21,000,000
Subsequent Event [Member]
Class of Stock [Line Items]
Common stock sold	23,353,000
Stock Awards [Member]
Class of Stock [Line Items]
Number of awards, Outstanding		2,605,423	2,557,842	2,557,842			2,605,423
Stock Options [Member]
Class of Stock [Line Items]
Adjusted exercise option price			$ 24.69	$ 24.69			$ 24.42
Number of options, Outstanding		4,673,829	4,108,535	4,108,535			4,673,829
Stock option exercisable			458,925