Preferred and Common Stock	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Stockholders' Equity Note Disclosure	Preferred and Common StockOn May 4, 2021, Arconic announced that its Board of Directors approved a share repurchase program authorizing the Company to repurchase shares of its outstanding common stock up to an aggregate transactional value of $300 over a two-year period expiring April 28, 2023. Repurchases under the program may be made from time to time, as the Company deems appropriate, solely through open market repurchases effected through a broker dealer, based on a variety of factors such as price, capital position, liquidity, financial performance, alternative uses of capital, and overall market conditions. There can be no assurance as to the number of shares the Company will repurchase. The share repurchase program may be increased or otherwise modified, renewed, suspended or terminated by the Company at any time, without prior notice. This program is intended to comply with Rule 10b5-1 and all purchases shall be made in compliance with Rule 10b-18, including without limitation the timing, price, and volume restrictions thereof. In the 2021 third quarter and nine-month period, Arconic repurchased 2,862,694 and 3,108,705 shares, respectively, of the Company's common stock for $97 and $106, respectively, under this program.