Statement of Changes in Consolidated Equity (unaudited) - USD ($) $ in Millions	Total	Preferred Class A	Preferred Class B	Preferred Stock	Mandatory Convertible Preferred Stock	Common Stock	Additional Capital	Retained Earnings (Accumulated Deficit)	Retained Earnings (Accumulated Deficit) Preferred Class A	Retained Earnings (Accumulated Deficit) Preferred Class B	Arconic	Noncontrolling Interests
Balance at Dec. 31, 2016	$ 5,141			$ 55	$ 3	$ 438	$ 8,214	$ (1,027)			$ (2,568)	$ 26
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	322							322				0
Other comprehensive income (J)	70										70	0
Cash dividends declared:
Preferred dividends declared, value		$ (1)	$ (16)						$ (1)	$ (16)
Common share, value	(54)							(54)
Stock-based compensation	28						28
Common stock issued: compensation plans	10					3	7
Distributions	(14)											(14)
Other	9							8				1
Balance at Mar. 31, 2017	5,495			55	3	441	8,249	(768)			(2,498)	13
Balance at Dec. 31, 2017	4,924			55	0	481	8,266	(1,248)			(2,644)	14
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	143							143				0
Other comprehensive income (J)	258										258	0
Cash dividends declared:
Preferred dividends declared, value		$ (1)							$ (1)
Common share, value	(58)							(58)
Stock-based compensation	15						15
Common stock issued: compensation plans	1					2	(1)
Balance at Mar. 31, 2018	$ 5,282			$ 55	$ 0	$ 483	$ 8,280	$ (1,164)			$ (2,386)	$ 14