Statement of Consolidated Operations (unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Sales (C)	$ 3,559	$ 3,524	$ 10,791	$ 10,542
Cost of goods sold (exclusive of expenses below)	2,800	2,881	8,557	8,552
Selling, general administrative, and other expenses	167	134	523	464
Research and development expenses	16	25	55	77
Provision for depreciation and amortization	131	141	407	427
Restructuring and other charges (D)	119	(2)	630	20
Operating income	326	345	619	1,002
Interest expense	86	88	256	291
Other expense, net (E)	31	8	92	69
Income before income taxes	209	249	271	642
Provision for income taxes (G)	114	88	110	218
Net income	95	161	161	424
Amounts Attributable to Arconic Common Shareholders (I):
Net income	$ 94	$ 160	$ 159	$ 422
Earning per share - basic (in usd per share)	$ 0.22	$ 0.33	$ 0.35	$ 0.87
Earning per share - diluted (in usd per share)	$ 0.21	$ 0.32	$ 0.35	$ 0.86
Average Shares Outstanding (I):
Average shares outstanding - basic (in shares)	436	483	451	483
Average shares outstanding - diluted (in shares)	457	502	455	503