Statement of Consolidated Operations - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Sales (B and C)	$ 14,014,000,000	$ 12,960,000,000	$ 12,394,000,000
Cost of goods sold (exclusive of expenses below)	11,397,000,000	10,221,000,000	9,696,000,000
Selling, general administrative, and other expenses	604,000,000	715,000,000	924,000,000
Research and development expenses	103,000,000	109,000,000	130,000,000
Provision for depreciation and amortization	576,000,000	551,000,000	535,000,000
Impairment of goodwill (A and O)	0	719,000,000	0
Restructuring and other charges (D)	9,000,000	165,000,000	155,000,000
Operating income	1,325,000,000	480,000,000	954,000,000
Interest expense (E)	378,000,000	496,000,000	499,000,000
Other expense (income), net (F)	(79,000,000)	486,000,000	(41,000,000)
Income from continuing operations before income taxes	868,000,000	470,000,000	414,000,000
Provision for income taxes (H)	226,000,000	544,000,000	1,476,000,000
Income (loss) from continuing operations after income taxes	642,000,000	(74,000,000)	(1,062,000,000)
Income from discontinued operations after income taxes (V)	0	0	184,000,000
Net income (loss)	642,000,000	(74,000,000)	(878,000,000)
Less: Net income from discontinued operations attributable to noncontrolling interests (V)	0	0	63,000,000
Net income (loss) Attributable to Arconic	642,000,000	(74,000,000)	(941,000,000)
Net income (loss)	$ 651,000,000	$ (127,000,000)	$ (1,010,000,000)
Earnings (loss) per share—basic:
Continuing operations (in usd per share)	$ 1.33	$ (0.28)	$ (2.58)
Discontinued operations (in usd per share)	0.00	0.00	0.27
Net loss per share-basic (in usd per share)	1.33	(0.28)	(2.31)
Earnings (loss) per share—diluted
Continuing operations (in usd per share)	1.30	(0.28)	(2.58)
Discontinued operations (in usd per share)	0.00	0.00	0.27
Net loss per share-diluted (in usd per share)	$ 1.30	$ (0.28)	$ (2.31)