Earnings Per Share - Reconciliation of Information Used to Compute Basic and Diluted EPS (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net income from continuing operations attributable to common shareholders	$ 80	$ 153
Income from discontinued operations	0	62
Net income	80	215
Less: preferred stock dividends declared	1	1
Net income available to Howmet Aerospace common shareholders - basic and diluted	$ 79	$ 214
Average shares outstanding - basic (in shares)	434	435
Effect of dilutive securities:
Stock options (in shares)	1	1
Stock and performance awards (in shares)	4	4
Average shares outstanding - diluted (in shares)	439	440