Property Transactions Narrative (Details) (USD $)	1 Months Ended	9 Months Ended	12 Months Ended						1 Months Ended
	Oct. 31, 2013 acre	Sep. 30, 2011 acre	Dec. 31, 2013	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2013 North Sea Assets Sold [Member]	Dec. 31, 2012 North Sea Assets Sold [Member]	May 31, 2011 Exit from Ecuador [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on Sale, Net of Tax			$ 65,000,000	$ 16,000,000		$ 0
Proceeds from Divestitures			327,000,000	1,160,000,000		77,000,000	56,000,000	117,000,000
Interest in Dumbarton and Lochranza Fields				30.00%
Net Book Value of Assets Sold								255,000,000
Asset Retirement Obligation								55,000,000
Income Tax Benefit Recognized								99,000,000
Exploration Expense				27,000,000
Land Exchanged In Agreement (in acres)	50,000
Cash Received For Reimbursement of Capital Expenditures and Other Normal Closing Adjustments	105,000,000
Ownership Percentage in Joint Venture with CONSOL		50.00%
Undeveloped Property (in acres)		628,000
Total Assets Acquired		1,300,000,000		1,258,000,000	[1]
Ratio of funding on share of future drilling and completion costs		one-third
Maximum amount to be paid each calendar year for funding of future drilling and completion costs		400,000,000
Funding of joint venture's future drilling and completion costs		2,100,000,000
Natural gas price agreed upon benchmark, average (in dollars per MMBtu)		4.00
Payable with imputed interest, discount				17,000,000
Cash Proceeds									73,000,000
Gain on Divestitures									$ 25,000,000

[1] Total reflects impact of $17 million imputed interest on CONSOL installment payments.