Cover Page - shares	6 Months Ended
	Jun. 30, 2019	Jul. 30, 2019
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2019
Document Transition Report	false
Entity File Number	1-3610
Entity Registrant Name	ARCONIC INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	25-0317820
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
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Common Stock, Shares Outstanding		440,188,364
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Entity Central Index Key	0000004281
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Common stock
Entity Information [Line Items]
Title of 12(b) Security	Common Stock, par value $1.00 per share
Trading Symbol	ARNC
Security Exchange Name	NYSE
Preferred stock
Entity 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