Income Taxes - Tax Years Subject to Examination by Major Jurisdiction Table (Detail)	12 Months Ended
	Dec. 31, 2011
United States [Member]
Income Tax Examination [Line Items]
Years under examination	2008-2011
China [Member]
Income Tax Examination [Line Items]
Years under examination	2006-2010
Algeria [Member]
Income Tax Examination [Line Items]
Years under examination	2008-2010
Ghana [Member]
Income Tax Examination [Line Items]
Years under examination	2006-2010