Income Taxes (Narrative) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) item MMBbls MMcf	Sep. 30, 2014	Sep. 30, 2015 USD ($) MMBbls MMcf	Sep. 30, 2014 USD ($)
Income Tax Examination [Line Items]
Income tax benefit from other foreign expenses | $				$ 0
Effective income tax rate	34.10%	31.60%	36.60%	43.70%
United States Tax [Member]
Income Tax Examination [Line Items]
Federal statutory income tax rate			35.00%
Earliest year remaining open for audit and/or settlement in major taxing jurisdictions			2011
Canada Tax [Member]
Income Tax Examination [Line Items]
Earliest year remaining open for audit and/or settlement in major taxing jurisdictions			2008
Malaysia Tax [Member]
Income Tax Examination [Line Items]
Federal statutory income tax rate			38.00%
Earliest year remaining open for audit and/or settlement in major taxing jurisdictions			2008
Number of marginal fields approved	3
Number of shallow-water blocks	2
Effective income tax rate			25.00%
Foreign tax benefit | $	$ 21,800,000		$ 21,800,000
United Kingdom Tax [Member]
Income Tax Examination [Line Items]
Earliest year remaining open for audit and/or settlement in major taxing jurisdictions			2012
Maximum [Member] | Malaysia Tax [Member] | Natural Gas Reserves [Member]
Income Tax Examination [Line Items]
Reserves | MMcf	500,000		500,000
Maximum [Member] | United Kingdom Tax [Member] | Oil Reserves [Member]
Income Tax Examination [Line Items]
Reserves | MMBbls	30		30