Earnings Per Share - Reconciliation of Information Used to Compute Basic and Diluted EPS (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Net income (loss) from continuing operations attributable to common shareholders	$ 74	$ (84)	$ 154	$ 69
(Loss) income from discontinued operations	0	(12)	0	50
Net income (loss)	74	(96)	154	119
Less: preferred stock dividends declared	1	0	1	1
Net income (loss) available to Howmet Aerospace common shareholders - basic and diluted	$ 73	$ (96)	$ 153	$ 118
Average shares outstanding - basic (in shares)	432	436	433	436
Effect of dilutive securities:
Stock options (in shares)	1	0	1	0
Stock and performance awards (in shares)	4	0	4	4
Average shares outstanding - diluted (in shares)	437	436	438	440