Statement of Changes in Consolidated Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Preferred Class A	Preferred stock	Common stock	Additional capital	Retained earnings (accumulated deficit)	Retained earnings (accumulated deficit) Cumulative Effect, Period of Adoption, Adjustment	Retained earnings (accumulated deficit) Preferred Class A	Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss Cumulative Effect, Period of Adoption, Adjustment	Noncontrolling Interests
Beginning balance at Dec. 31, 2017	$ 4,908	$ 0		$ 55	$ 481	$ 8,266	$ (1,264)	$ 367		$ (2,644)	$ (367)	$ 14
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	642						642
Other comprehensive income (loss) (L)	85									85
Cash dividends declared:
Cash dividends declared, preferred			$ (2)						$ (2)
Cash dividends declared, common	(117)						(117)
Stock-based compensation (J)	50					50
Common stock issued: compensation plans (J)	5				2	3
Other	(2)											(2)
Ending balance at Dec. 31, 2018	5,569	$ 73		55	483	8,319	(374)	$ 75		(2,926)	$ (2)	12
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	470						470
Other comprehensive income (loss) (L)	(401)									(401)
Cash dividends declared:
Cash dividends declared, preferred			(2)						(2)
Cash dividends declared, common	(56)						(56)
Stock-based compensation (J)	57					57
Common stock issued: compensation plans (J)	41				5	36
Repurchase and retirement of common stock (J)	(1,150)				(55)	(1,095)
Other	4					2						2
Ending balance at Dec. 31, 2019	4,605			55	433	7,319	113			(3,329)		14
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	261						261
Other comprehensive income (loss) (L)	16									16
Cash dividends declared:
Cash dividends declared, preferred			$ (2)						$ (2)
Cash dividends declared, common	(8)						(8)
Stock-based compensation (J)	45					45
Common stock issued: compensation plans (J)	(6)				3	(9)
Repurchase and retirement of common stock (J)	(73)				(3)	(70)
Distribution to Arconic Corporation (C)	(1,261)					(2,617)				1,370		(14)
Ending balance at Dec. 31, 2020	$ 3,577			$ 55	$ 433	$ 4,668	$ 364			$ (1,943)		$ 0