Cover - shares	9 Months Ended
	Sep. 30, 2021	Nov. 01, 2021
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	1-3610
Entity Registrant Name	HOWMET AEROSPACE INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	25-0317820
Entity Address, Address Line One	201 Isabella Street, Suite 200
Entity Address, City or Town	Pittsburgh
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	15212-5872
City Area Code	412
Local Phone Number	553-1940
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		427,217,982
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Entity Central Index Key	0000004281
Current Fiscal Year End Date	--12-31
Common stock
Entity Information [Line Items]
Title of 12(b) Security	Common Stock, par value $1.00 per share
Trading Symbol	HWM
Security Exchange Name	NYSE
Preferred stock
Entity Information [Line Items]
Title of 12(b) Security	$3.75 Cumulative Preferred Stock, par value $100.00 per share
Trading Symbol	HWM PR
Security Exchange Name	NYSEAMER