Statement of Changes in Consolidated Equity (unaudited) - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Capital [Member]	Retained Earnings (Deficit) [Member]	Accumulated Other Comprehensive Loss [Member]	Non-controlling Interest [Member]
Balance at Dec. 31, 2020	$ 5,016	$ 2	$ 9,663	$ (725)	$ (5,629)	$ 1,705
Net income	219			175		44
Other comprehensive (loss) income	(311)				(249)	(62)
Stock-based compensation	8		8
Common stock issued: compensation plans	4		4
Distributions	(62)					(62)
Other	(1)		(1)
Balance at Mar. 31, 2021	4,873	2	9,674	(550)	(5,878)	1,625
Balance at Dec. 31, 2020	5,016	2	9,663	(725)	(5,629)	1,705
Net income	939
Other comprehensive (loss) income	(370)
Balance at Sep. 30, 2021	5,461	2	9,708	96	(5,928)	1,583
Balance at Mar. 31, 2021	4,873	2	9,674	(550)	(5,878)	1,625
Net income	350			309		41
Other comprehensive (loss) income	250				191	59
Stock-based compensation	10		10
Common stock issued: compensation plans	10		10
Distributions	(75)					(75)
Other			1			(1)
Balance at Jun. 30, 2021	5,418	2	9,695	(241)	(5,687)	1,649
Net income	370			337		33
Other comprehensive (loss) income	(309)				(241)	(68)
Stock-based compensation	8		8
Common stock issued: compensation plans	5		5
Contributions	8					8
Distributions	(40)					(40)
Other	1					1
Balance at Sep. 30, 2021	5,461	2	9,708	96	(5,928)	1,583
Balance at Dec. 31, 2021	6,284	2	9,577	(315)	(4,592)	1,612
Net income	553			469		84
Other comprehensive (loss) income	(382)				(482)	100
Stock-based compensation	9		9
Common stock issued: compensation plans	2		2
Repurchase of common stock	(75)		(54)	(21)
Dividends paid on Alcoa common stock	(19)			(19)
Contributions	46					46
Distributions	(162)					(162)
Other	1		3			(2)
Balance at Mar. 31, 2022	6,257	2	9,537	114	(5,074)	1,678
Balance at Dec. 31, 2021	6,284	2	9,577	(315)	(4,592)	1,612
Net income	458
Other comprehensive (loss) income	842
Balance at Sep. 30, 2022	6,892	2	9,171	(158)	(3,644)	1,521
Balance at Mar. 31, 2022	6,257	2	9,537	114	(5,074)	1,678
Net income	674			549		125
Other comprehensive (loss) income	688				819	(131)
Stock-based compensation	11		11
Common stock issued: compensation plans	1		1
Repurchase of common stock	(275)		(236)	(39)
Dividends paid on Alcoa common stock	(18)			(18)
Contributions	37					37
Distributions	(83)					(83)
Balance at Jun. 30, 2022	7,292	2	9,313	606	(4,255)	1,626
Net income	(769)			(746)		(23)
Other comprehensive (loss) income	536				611	(75)
Stock-based compensation	8		8
Repurchase of common stock	(150)		(150)
Dividends paid on Alcoa common stock	(18)			(18)
Contributions	67					67
Distributions	(74)					(74)
Balance at Sep. 30, 2022	$ 6,892	$ 2	$ 9,171	$ (158)	$ (3,644)	$ 1,521