| Cover | Aug. 06, 2019 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 6, 2019 |
| Entity File Number | 1-3610 |
| Entity Registrant Name | ARCONIC INC. |
| Entity Central Index Key | 0000004281 |
| Entity Tax Identification Number | 25-0317820 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 201 Isabella Street |
| Entity Address, Address Line Two | Suite 200 |
| Entity Address, City or Town | Pittsburgh |
| Entity Address, State or Province | PA |
| Entity Address, Postal Zip Code | 15212-5872 |
| City Area Code | 212 |
| Local Phone Number | 836-2732 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Common Stock | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common Stock, par value $1.00 per share |
| Trading Symbol | ARNC |
| Security Exchange Name | NYSE |
| Preferred Class A | |
| Document Information [Line Items] | |
| Title of 12(b) Security | $3.75 Cumulative Preferred Stock, par value $100 per share |
| Trading Symbol | ARNC PR |
| Security Exchange Name | NYSEAMER |
