Income Taxes - Tax Years Subject to Examination by Major Jurisdiction Table (Detail)	12 Months Ended
	Dec. 31, 2012
United States [Member] | Examination Year One [Member]
Income TaxExamination [Line Items]
Tax year subject to examination	2007
United States [Member] | Examination Year Two [Member]
Income TaxExamination [Line Items]
Tax year subject to examination	2008
United States [Member] | Examination Year Three [Member]
Income TaxExamination [Line Items]
Tax year subject to examination	2010
United States [Member] | Examination Year Four [Member]
Income TaxExamination [Line Items]
Tax year subject to examination	2011
United States [Member] | Examination Year Five [Member]
Income TaxExamination [Line Items]
Tax year subject to examination	2012
China [Member] | Minimum [Member]
Income TaxExamination [Line Items]
Tax year subject to examination	2008
China [Member] | Maximum [Member]
Income TaxExamination [Line Items]
Tax year subject to examination	2012
Algeria [Member] | Minimum [Member]
Income TaxExamination [Line Items]
Tax year subject to examination	2009
Algeria [Member] | Maximum [Member]
Income TaxExamination [Line Items]
Tax year subject to examination	2012
Ghana [Member] | Minimum [Member]
Income TaxExamination [Line Items]
Tax year subject to examination	2006
Ghana [Member] | Maximum [Member]
Income TaxExamination [Line Items]
Tax year subject to examination	2011