Statement of Consolidated Operations (unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Sales (C)	$ 3,691	$ 3,573	$ 7,232	$ 7,018
Cost of goods sold (exclusive of expenses below)	2,939	2,903	5,757	5,671
Selling, general administrative, and other expenses	178	158	356	330
Research and development expenses	17	29	39	52
Provision for depreciation and amortization	139	144	276	286
Restructuring and other charges (D)	499	15	511	22
Operating (loss) income	(81)	324	293	657
Interest expense	85	89	170	203
Other expense, net (E)	29	41	61	61
(Loss) income before income taxes	(195)	194	62	393
(Benefit) provision for income taxes (G)	(74)	74	(4)	130
Net (loss) income	(121)	120	66	263
Amounts Attributable to Arconic Common Shareholders (I):
Net (loss) income	$ (121)	$ 120	$ 65	$ 262
(Loss) earnings per share - basic (in usd per share)	$ (0.27)	$ 0.25	$ 0.14	$ 0.54
(Loss) earnings per share - diluted (in usd per share)	$ (0.27)	$ 0.24	$ 0.14	$ 0.53
Average Shares Outstanding (I):
Average shares outstanding - basic (in shares)	445	483	458	483
Average shares outstanding - diluted (in shares)	445	502	462	502