Other Financial Information - Additional Information (Detail) - USD ($) $ in Millions		1 Months Ended	12 Months Ended
	Oct. 31, 2016	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Non operating Income Expense [Line Items]
Net gain from asset sales			$ 116	$ 164	$ 32
Increase (decrease) in restricted cash				(1,226)
Yadkin [Member]
Other Non operating Income Expense [Line Items]
Net gain from asset sales			$ 122
Alcoa Nederland Holding BV [Member]
Other Non operating Income Expense [Line Items]
Senior notes issued		$ 1,250
Net proceeds from issuance of senior notes		1,228
Restricted cash		$ 1,228
Increase (decrease) in restricted cash	$ (1,228)
Disposal of Equity Interests [Member]
Other Non operating Income Expense [Line Items]
Net gain from asset sales				27
Disposal of Land [Member]
Other Non operating Income Expense [Line Items]
Net gain from asset sales				$ 118	$ 29