Divestitures (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Discontinued Operation, Income (Loss) from Discontinued Operation Disclosures [Abstract]
Oil and Gas Sales	$ 11	$ 54	$ 32	$ 194
Income Before Income Taxes	7	38	10	117
Income Tax Expense	(3)	3	7	50
Operating Income (Loss), Net of Tax	10	35	3	67
Gain on Sale, Net of Tax	0	22	55	22
Discontinued Operations, Net of Tax	10	57	58	89
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales Proceeds			119	1,161
Asset Retirement Obligations Associated with Assets Sold			15	98
Gain on Divestitures	0	157	12	167
North Sea Assets Sold [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales Proceeds			54
US Onshore Assets Sold [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales Proceeds			60
Net Book Value of Assets Sold			(53)
Goodwill Allocated to Assets Sold			(4)
Asset Retirement Obligations Associated with Assets Sold			5
Other Closing Adjustments			4
Gain on Divestitures			$ 12