Debt - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended		6 Months Ended	3 Months Ended		6 Months Ended		6 Months Ended	3 Months Ended						6 Months Ended
	Jun. 30, 2013 SecurityLoan D	Mar. 31, 2013 Agreement	Jun. 30, 2013 D	Jun. 30, 2012	Jan. 31, 2013	Jan. 31, 2012	Jun. 30, 2013 Credit Facility Maturing March 2014 [Member]	Mar. 31, 2013 Aluminio [Member] D	Jun. 30, 2013 6% Notes, Due 2013 [Member]	May 31, 2013 6% Notes, Due 2013 [Member]	Jun. 30, 2013 Debt Accrued And Unpaid Interest [Member]	Mar. 31, 2013 Term Loan Agreement [Member]	Mar. 31, 2013 Term Loan Agreement [Member] First Loans Agreement [Member]	Jun. 30, 2013 Revolving Credit Agreement [Member]	Mar. 31, 2013 Revolving Credit Agreement [Member]	Jun. 30, 2013 Revolving Credit Agreement [Member] First Loans Agreement [Member]	Jun. 30, 2013 Revolving Credit Agreement [Member] First Credit Facility [Member]	Mar. 31, 2013 Revolving Credit Agreement [Member] First Credit Facility [Member]	Jun. 30, 2013 Revolving Credit Agreement [Member] Second Credit Facility [Member]	Mar. 31, 2013 Revolving Credit Agreement [Member] Second Credit Facility [Member]	Jun. 30, 2013 Revolving Credit Agreement [Member] Third Credit Facility [Member]	Mar. 31, 2013 Revolving Credit Agreement [Member] Third Credit Facility [Member]	Jun. 30, 2013 Revolving Credit Agreement [Member] Second Loans Agreement [Member]	Jun. 30, 2013 Revolving Credit Agreement [Member] Third Loans Agreement [Member]
Debt Instrument [Line Items]
Early repayment of outstanding notes										$ 422
Long-term debt, interest rate						6.00%				6.00%
Line of credit facility, amount outstanding		200	1,647	659				52	435		12	200
Purchase premiums repaid recorded as interest expense			1
Line of credit facility amount outstanding					150			52				200	200
Repayment of credit facility							150
Borrowing under revolving credit facility																	200	200
Agreed credit facility amount																			150	150	75	75
Number of agreements		3
Line of credit facility, amount outstanding															$ 200
Line of credit facility, expiration date																Jul. 31, 2013							Feb. 28, 2014	Dec. 31, 2013
Revolving credit facility, term														5 years
Number of borrowing arrangements	6
Number of active borrowing arrangements	4
Number of terminated borrowing arrangements	2
Weighted-average interest rate	1.58%		1.50%					0.72%
Weighted-average days outstanding	40		72					70