Summary Of Significant Accounting Policies (Weighted-Average Useful Lives Of Structures And Machinery And Equipment) (Details)	12 Months Ended
	Dec. 31, 2011
Structures [Member] | Alumina [Member]
Property, Plant and Equipment [Line Items]
Weighted-average useful lives of assets, years	29
Structures [Member] | Primary Metals [Member]
Property, Plant and Equipment [Line Items]
Weighted-average useful lives of assets, years	34
Structures [Member] | Flat-Rolled Products [Member]
Property, Plant and Equipment [Line Items]
Weighted-average useful lives of assets, years	31
Structures [Member] | Engineered Products And Solutions [Member]
Property, Plant and Equipment [Line Items]
Weighted-average useful lives of assets, years	27
Machinery And Equipment [Member] | Alumina [Member]
Property, Plant and Equipment [Line Items]
Weighted-average useful lives of assets, years	25
Machinery And Equipment [Member] | Primary Metals [Member]
Property, Plant and Equipment [Line Items]
Weighted-average useful lives of assets, years	21
Machinery And Equipment [Member] | Flat-Rolled Products [Member]
Property, Plant and Equipment [Line Items]
Weighted-average useful lives of assets, years	21
Machinery And Equipment [Member] | Engineered Products And Solutions [Member]
Property, Plant and Equipment [Line Items]
Weighted-average useful lives of assets, years	18