Statement of Consolidated Operations (unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Sales (C & D)	$ 3,445	$ 3,192
Cost of goods sold (exclusive of expenses below)	2,768	2,458
Selling, general administrative, and other expenses	172	217
Research and development expenses	23	28
Provision for depreciation and amortization	142	133
Restructuring and other charges (E)	7	73
Operating income	333	283
Interest expense (N)	114	115
Other expense (income), net (F)	20	(316)
Income before income taxes	199	484
Provision for income taxes (H)	56	162
Net income	143	322
Amounts Attributable to Arconic Common Shareholders (I):
Net income	$ 142	$ 305
Earnings per share - basic
Earnings per share - basic (in usd per share)	$ 0.30	$ 0.69
Earnings per share - diluted
Earnings per share - diluted (in usd per share)	0.29	0.65
Dividends paid per share (in usd per share)	$ 0.06	$ 0.06
Weighted Average Shares Outstanding (J):
Average shares outstanding - basic (in shares)	482	440
Average shares outstanding - diluted (in shares)	503	499