Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 BusinessTaxProvision	Jun. 30, 2012	Dec. 31, 2012
Income Taxes [Line Items]
Effective tax rate	16.50%	216.70%	79.40%	39.40%
U.S federal statutory rate	35.00%	35.00%	35.00%	35.00%
Nondeductible charge	$ 103
Charge related to non-deductible depletion		8
Charge related to other miscellaneous items		2
Number of specific temporary business tax provisions expired during the period			2
Tax provision due to two specific temporary business tax provision that expired in 2011					19
Spain and Australia Authority [Member]
Income Taxes [Line Items]
Charge resulting from prior years taxes in Spain and Australia	10		10
U.S. [Member]
Income Taxes [Line Items]
Charge resulting from prior years taxes in Spain and Australia			19
Italy [Member]
Income Taxes [Line Items]
Nondeductible expense tax benefit	$ 0