Statement of Consolidated Operations (unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Sales (C & D)	$ 3,573	$ 3,261	$ 7,018	$ 6,453
Cost of goods sold (exclusive of expenses below)	2,903	2,549	5,671	5,007
Selling, general administrative, and other expenses	158	200	330	417
Research and development expenses	29	29	52	57
Provision for depreciation and amortization	144	137	286	270
Restructuring and other charges (E)	15	26	22	99
Operating income	324	320	657	603
Interest expense (N)	89	183	203	298
Other expense (income), net (F)	41	(132)	61	(448)
Income before income taxes	194	269	393	753
Provision for income taxes (H)	74	57	130	219
Net income	120	212	263	534
Amounts Attributable to Arconic Common Shareholders (I):
Net income	$ 120	$ 194	$ 262	$ 499
Earnings per share - basic (in usd per share)	$ 0.25	$ 0.44	$ 0.54	$ 1.13
Earnings per share - diluted (in usd per share)	0.24	0.43	0.53	1.07
Dividends paid per share (in usd per share)	$ 0.06	$ 0.06	$ 0.12	$ 0.12
Weighted Average Shares Outstanding (J):
Average shares outstanding - basic (in shares)	483	441	483	440
Average shares outstanding - diluted (in shares)	502	462	502	500