Restructuring and Other Charges - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012 Person
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 7	$ 10
Restructuring and other charges, after-tax and noncontrolling interests	5	7
Number of employees associated with layoff costs		220
Minimum amount of cash payments expected to be paid beyond the end of the current annual period	50
Maximum amount of cash payments expected to be paid beyond the end of the current annual period	55
Primary Metals [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		5
Number of employees associated with layoff costs	60	150
Engineered Products and Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	3	3
Number of employees associated with layoff costs		70
Other Miscellaneous Items [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, other adjustment	4	1
Restructuring reserve, other adjustment, after-tax	3	1
Layoff Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	3	11
Restructuring and other charges, after-tax and noncontrolling interests	2	8
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
Small Layoff Reserves Related to Prior Periods [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, other adjustment		2
Restructuring reserve, other adjustment, after-tax		2
Restructuring Programs Layoffs 2013 [Member]
Restructuring Cost and Reserve [Line Items]
Cash payments made against the layoff reserves	1
Restructuring Programs Layoffs 2012 [Member]
Restructuring Cost and Reserve [Line Items]
Total number of employees already laid off	400
Number of positions separated	800
Cash payments made against the layoff reserves	7
Restructuring Programs Layoffs 2011 [Member]
Restructuring Cost and Reserve [Line Items]
Total number of employees already laid off	900
Number of positions separated	1,475
Cash payments made against the layoff reserves	$ 4