Segment Information (Schedule Of Operating Results Of Reportable Segments) (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Third-party sales	$ 6,350	$ 5,223	$ 18,805	$ 15,179
Intersegment sales	1,597	1,141	4,845	3,664
Total sales	7,947	6,364	23,650	18,843
Equity income (loss)	(2)	2	24	10
Depreciation, depletion, and amortization	355	336	1,050	1,019
Income taxes	156	64	570	275
After-tax operating income (ATOI)	462	328	1,652	1,015
Alumina [Member]
Third-party sales	879	717	2,615	2,056
Intersegment sales	751	506	2,107	1,627
Total sales	1,630	1,223	4,722	3,683
Equity income (loss)	2	1	27	7
Depreciation, depletion, and amortization	117	100	332	299
Income taxes	42	(22)	146	46
After-tax operating income (ATOI)	154	70	482	236
Primary Metals [Member]
Third-party sales	2,124	1,688	6,249	5,100
Intersegment sales	798	589	2,559	1,905
Total sales	2,922	2,277	8,808	7,005
Equity income (loss)	(4)		(4)	1
Depreciation, depletion, and amortization	137	142	420	431
Income taxes	21	(3)	129	15
After-tax operating income (ATOI)	110	78	513	310
Flat-Rolled Products [Member]
Third-party sales	1,974	1,645	5,951	4,654
Intersegment sales	48	46	179	132
Total sales	2,022	1,691	6,130	4,786
Depreciation, depletion, and amortization	61	57	179	173
Income taxes	26	26	94	72
After-tax operating income (ATOI)	60	66	240	167
Engineered Products and Solutions [Member]
Third-party sales	1,373	1,173	3,990	3,369
Total sales	1,373	1,173	3,990	3,369
Equity income (loss)		1	1	2
Depreciation, depletion, and amortization	40	37	119	116
Income taxes	67	63	201	142
After-tax operating income (ATOI)	$ 138	$ 114	$ 417	$ 302