Goodwill and Other Intangible Assets - Summary of Goodwill which is Included in Other Noncurret Assets (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Goodwill [Line Items]
Goodwill	$ 142	$ 146
Other Noncurrent Assets [Member]
Goodwill [Line Items]
Goodwill	142	146
Corporate Segment [Member]
Goodwill [Line Items]
Accumulated impairment losses	742	742
Corporate Segment [Member] | Other Noncurrent Assets [Member]
Goodwill [Line Items]
Goodwill	139	142
Alumina [Member] | Other Noncurrent Assets [Member]
Goodwill [Line Items]
Goodwill	$ 3	$ 4