Asset Retirement Obligations (Schedule Of Carrying Value Of Recorded AROs By Major Category) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Asset Retirement Obligations [Abstract]
Spent pot lining disposal	$ 187		$ 177
Closure of bauxite residue areas	173		156
Mine reclamation	164		156
Demolition	34	[1]	24	[1]
Landfill closure	17		19
Other	4		2
Asset retirement obligation, total	$ 579		$ 534		$ 453

[1] In 2011 and 2010, AROs were recorded as a result of management's decision to permanently shut down and demolish certain structures, each of which was previously temporarily idled for different reasons (see Note D).