Income Taxes (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Examination [Line Items]
Income tax benefits attributable to employee stock option transactions	$ 5,364,000	$ 7,435,000	$ 5,920,000
Decrease in deferred tax asset valuation allowance	327,272,000
Undistributed earnings of subsidiaries considered indefinitely invested	6,045,000,000
Unrecognized deferred tax liability	684,000,000
Withholding tax on any monies repatriated from Canada to the U.S.	5.00%
Other recorded liabilities for interest and penalties	142,000	146,000
Income tax expense, (charges) net benefits for interest and penalties	4,000	829,000	1,000
Expected liability to be added for uncertain taxes during next twelve months	1,000,000
Expected liability to be added for uncertain taxes during next twelve months	2,000,000
United States [Member]
Income Tax Examination [Line Items]
Earliest year remaining open for audit and/or settlement in major taxing jurisdictions	2011
Canada [Member]
Income Tax Examination [Line Items]
Earliest year remaining open for audit and/or settlement in major taxing jurisdictions	2008
United Kingdom [Member]
Income Tax Examination [Line Items]
Earliest year remaining open for audit and/or settlement in major taxing jurisdictions	2012
Repatriated cash	250,000,000
Malaysia [Member]
Income Tax Examination [Line Items]
Earliest year remaining open for audit and/or settlement in major taxing jurisdictions	2007
Repatriated cash	1,700,000,000
Percentage of interest in oil and gas property sold during period	20.00%
Block H Development Plan [Member]
Income Tax Examination [Line Items]
Decrease in deferred tax asset valuation allowance	$ 65,384,000
Foreign Country [Member] | Minimum [Member]
Income Tax Examination [Line Items]
Foreign tax credit carryforwards expiration year	2015
Foreign Country [Member] | Maximum [Member]
Income Tax Examination [Line Items]
Foreign tax credit carryforwards expiration year	2024