Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Jun. 30, 2012
Income Tax Examination [Line Items]
U.S. Federal statutory income tax rate			35.00%
United Kingdom, corporation tax rate	25.00%	24.00%
United Kingdom, corporation tax rate, tax relief on oil and gas decommissioning costs	50.00%	62.00%
April 1, 2013
Income Tax Examination [Line Items]
United Kingdom, corporation tax rate	23.00%
Third quarter 2012
Income Tax Examination [Line Items]
United Kingdom, net increase to tax expenses	7
United States
Income Tax Examination [Line Items]
Earliest year remaining open for audit and/or settlement in major taxing jurisdictions			2008
Canada
Income Tax Examination [Line Items]
Earliest year remaining open for audit and/or settlement in major taxing jurisdictions			2007
United Kingdom
Income Tax Examination [Line Items]
Earliest year remaining open for audit and/or settlement in major taxing jurisdictions			2010
Malaysia
Income Tax Examination [Line Items]
Earliest year remaining open for audit and/or settlement in major taxing jurisdictions			2006