Segment Information (Operating Results Of Reportable Segments) (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Third-party sales	$ 6,526	$ 5,107	$ 12,455	$ 9,956
Intersegment sales	1,707	1,263	3,248	2,523
Total sales	8,233	6,370	15,703	12,479
Equity income (loss)	21	5	26	8
Depreciation, depletion, and amortization	355	344	695	683
Income taxes	222	117	414	211
After-tax operating income (ATOI)	635	381	1,190	687
Alumina [Member]
Third-party sales	926	701	1,736	1,339
Intersegment sales	723	530	1,356	1,121
Total sales	1,649	1,231	3,092	2,460
Equity income (loss)	22	4	25	6
Depreciation, depletion, and amortization	112	107	215	199
Income taxes	60	41	104	68
After-tax operating income (ATOI)	186	94	328	166
Primary Metals [Member]
Third-party sales	2,145	1,710	4,125	3,412
Intersegment sales	922	693	1,761	1,316
Total sales	3,067	2,403	5,886	4,728
Equity income (loss)	(1)	1		1
Depreciation, depletion, and amortization	142	142	283	289
Income taxes	55		108	18
After-tax operating income (ATOI)	201	109	403	232
Flat-Rolled Products [Member]
Third-party sales	2,085	1,574	3,977	3,009
Intersegment sales	62	40	131	86
Total sales	2,147	1,614	4,108	3,095
Depreciation, depletion, and amortization	60	57	118	116
Income taxes	35	28	68	46
After-tax operating income (ATOI)	99	71	180	101
Engineered Products and Solutions [Member]
Third-party sales	1,370	1,122	2,617	2,196
Total sales	1,370	1,122	2,617	2,196
Equity income (loss)			1	1
Depreciation, depletion, and amortization	41	38	79	79
Income taxes	72	48	134	79
After-tax operating income (ATOI)	$ 149	$ 107	$ 279	$ 188