Other Expenses (Income), Net - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other Non operating Income Expense [Line Items]
Net gain from asset sales	$ (1)	$ 132	$ 115	$ 164
Natural Gas Pipeline [Member] | Australia [Member]
Other Non operating Income Expense [Line Items]
Net gain from asset sales				27
Yadkin [Member]
Other Non operating Income Expense [Line Items]
Net gain from asset sales			$ 120
Wharf Property Near Intalco, WA smelter [Member]
Other Non operating Income Expense [Line Items]
Net gain from asset sales		$ 118		$ 118