Asset Retirement Obligations - Schedule of Carrying Value of Recorded AROs by Major Category (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Asset Retirement Obligation Disclosure [Abstract]
Spent pot lining disposal	$ 141	$ 170
Closure of bauxite residue areas	165	178
Mine reclamation	191	167
Demolition	117	114
Landfill closure	30	31
Other	4	3
Asset retirement obligation, total	$ 648	$ 663	$ 629