Restructuring And Other Charges (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012 employee	Mar. 31, 2011 employee	Dec. 31, 2011
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 10	$ 6
Restructuring and other charges, after-tax and noncontrolling interests	7	5
Number of employees associated with layoff costs	220	360
Restructuring reserve, other adjustment		2
Restructuring reserve, other adjustment, after-tax		1
Cash payments	15		54
Minimum amount of cash payments expected to be paid beyond the end of the current annual period	45
Maximum amount of cash payments expected to be paid beyond the end of the current annual period	50
Engineered Products And Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	3
Number of employees associated with layoff costs	70
Primary Metals [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	5	2
Number of employees associated with layoff costs	150
Global Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	1	2
Number of employees associated with layoff costs		350
Other Miscellaneous Charges [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, other adjustment	1
Restructuring reserve, other adjustment, after-tax	1
Alumina [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		1
Number of employees associated with layoff costs		10
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	1	1
Other Exit Costs [Member]
Restructuring Cost and Reserve [Line Items]
Cash payments	2		9
Small Layoff Reserves Related To Prior Periods [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, other adjustment	2	2
Restructuring reserve, other adjustment, after-tax	2	1
Charges From On-Going Activity [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, other adjustment		1
Restructuring reserve, other adjustment, after-tax		1
Layoff Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	11	5
Restructuring and other charges, after-tax and noncontrolling interests	8	4
Cash payments	13		45
Smelter Curtailments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	6
Restructuring and other charges, after-tax and noncontrolling interests	4
Number of employees associated with layoff costs	150
Restructuring Programs (Layoffs), 2012 [Member]
Restructuring Cost and Reserve [Line Items]
Cash payments	2
Total number of employees already laid off	10
Number of positions terminated	220
Restructuring Programs (Layoffs), 2011 [Member]
Restructuring Cost and Reserve [Line Items]
Cash payments	8
Total number of employees already laid off	400
Number of positions terminated	1,600
Restructuring Programs (Layoffs), 2010 [Member]
Restructuring Cost and Reserve [Line Items]
Cash payments	$ 2
Total number of employees already laid off	800
Number of positions terminated	875
Restructuring Programs (Layoffs), 2009 [Member]
Restructuring Cost and Reserve [Line Items]
Total number of employees already laid off	5,750
Number of positions terminated	6,000