Income Taxes - Reconciliation of US Statutory Federal Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule Of Income Taxes [Line Items]
US statutory federal rate	35.00%	35.00%	35.00%
Non-US income taxed at different rates	(10.00%)	(10.00%)	(14.00%)
Charges and credit (See Note 3)			(3.00%)
Other	(1.00%)	(1.00%)	(1.00%)
Effective income tax rate	24.00%	24.00%	17.00%