Divestitures (Details) $ in Millions			3 Months Ended
		May 01, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($) well	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration				$ 300
Proceeds Allocated to Undeveloped Leasehold Cost				$ 246
Percentage of divestiture farmed out				35.00%		35.00%
Sales Proceeds				$ 40	$ 232
Accounts and Other Receivables, Net, Current	[1]			$ 0		$ 40
Number Of Wells | well				7
Number of Wells Operated by Company | well				4
2016 Asset Sales [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales Proceeds					20
Marcellus Shale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Assets				$ 3,300
Alon A And Alon C [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total transaction value					$ 73
Percentage of divestiture farmed out					47.00%
Disposal Group, Including Discontinued Operation, Assets					$ 67
Disposal Group, Including Discontinued Operations, Adjustment To Consideration					$ 6
Cyprus Block 12 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds received from farm-out agreement				131
Accounts and Other Receivables, Net, Current				$ 40
Subsequent Event [Member] | Marcellus Shale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total transaction value		$ 1,200
Sales Proceeds		1,100
Disposal Group, Including Discontinued Operations, Adjustment To Consideration		$ 100
Scenario, Forecast [Member] | Marcellus Shale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (Loss) on Disposition of Assets			$ 2,200

[1] 35%