Acquisitions, Divestitures and Merger - Narrative (Details)							1 Months Ended		3 Months Ended	5 Months Ended	12 Months Ended
	Jan. 31, 2018 USD ($) a bbl / d mi bbl	Jan. 29, 2018 USD ($) shares	Jun. 28, 2017 USD ($) payment $ / MMBTU	Jun. 26, 2017 USD ($) a shares	Apr. 03, 2017 USD ($) bbl / d mi bbl	Jul. 20, 2015 USD ($) a business shares	Jan. 31, 2018 USD ($)	Jan. 31, 2017 USD ($) well	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2017 USD ($) a MMcf / d shares	Dec. 31, 2016 USD ($) a shares	Dec. 31, 2015 USD ($)	Feb. 15, 2018 USD ($)	Jan. 28, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales Proceeds											$ 2,073,000,000	$ 1,241,000,000	$ 151,000,000
Loss on Marcellus Shale Upstream Divestiture											2,379,000,000	$ 0	0
Exit costs											41,000,000
Commitment to third party for assumption of retained capacity											$ 52,000,000
Ownership interest sold									35.00%		35.00%	35.00%
Asset retirement obligation									$ 935,000,000	$ 989,000,000	$ 875,000,000	$ 935,000,000	989,000,000
Gain (loss) on disposition of assets											326,000,000	238,000,000	0
Cash paid											616,000,000	0	0
Equity Method Investments									400,000,000	453,000,000	$ 305,000,000	$ 400,000,000	453,000,000
Stock issued (shares) | shares											54,087,136	0
Proceeds from issuance of common limited partners units											$ 312,000,000	$ 299,000,000	0
Proceeds from debt											325,000,000	0	0
Gain (loss) on divestitures											326,000,000	238,000,000	0
Severance, consulting, investment, advistory, legal and other related merger-related fees											100,000,000	0	$ 0
Revenue since acquisition										181,000,000		457,000,000
Pre-tax loss since acquisition										120,000,000		20,000,000
Purchase price allocation adjustment										$ 163,000,000		$ 25,000,000
Marcellus Shale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total consideration value			$ 1,200,000,000
Sales Proceeds			1,000,000,000
Consideration adjustment			$ 100,000,000
Additional consideration, number of payments, divestiture | payment			3
Additional consideration, Individual payment amounts			$ 33,300,000
Minimum Appalachia Dominion, South Point index price for contingent consideration to be required ($ per MMBtu) | $ / MMBTU			3.30
Loss on Marcellus Shale Upstream Divestiture											2,400,000,000
Loss on sale of property, after tax											$ 1,500,000,000
Asset consideration			$ 3,400,000,000
Natural gas production per day | MMcf / d											204
Southwest Royalties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity method investment, amount sold											$ 102,000,000
Asset retirement obligation											42,000,000
Onshore US
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses											671,000,000
Proceeds expected from divestiture											40,000,000
DJ Basin (Onshore US)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses											568,000,000
Mineral and Royalty Assets
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales Proceeds											335,000,000
Gain (loss) on disposition of assets											$ 334,000,000
Mineral and royalty assets, area | a											140,000
CONE Gathering LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership percentage											50.00%
Equity Method Investments											$ 181,000,000
CONSOL Carried Cost Obligation
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash remitted									213,000,000
Wells Ranch Development Area
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Land exchanged (acres) | a												11,700
Bronco Development Area
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Land sold (acres) | a												13,500
Tamar Field, Offshore Israel
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total consideration value									$ 431,000,000			$ 431,000,000
Sales Proceeds												$ 316,000,000
Ownership interest sold									3.50%			3.50%
Gain (loss) on divestitures												$ 261,000,000
Ownership percentage required per agreement									25.00%			25.00%
Delaware Basin
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of wells | well								7
Consideration transferred								$ 301,000,000
Proceeds allocated to undeveloped leasehold cost								246,000,000
Cash paid									$ 30,000,000
Rosetta Resources, Inc
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Stock issued (shares) | shares						41,000,000
Number of businesses acquired | business						2
Merger-related costs incurred						$ 81,000,000
Severance, consulting, investment, advistory, legal and other related merger-related fees						66,000,000
Noncash share-based compensation expense						$ 15,000,000
Common Stock | Rosetta Resources, Inc
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Business combination, stock exchange ratio						0.542
Delaware Basin Area | Rosetta Resources, Inc
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gas and oil area acquired | a						45,000
Midland Basin | Rosetta Resources, Inc
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gas and oil area acquired | a						9,000
Long-term debt, fair value						$ 2,000,000,000
Eagle Ford Shale | Rosetta Resources, Inc
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gas and oil area acquired | a						50,000
Delaware Basin | Rosetta Resources, Inc
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gas and oil area acquired | a						54,000
Noble Midstream Partners LP | Blanco River DevCo
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest acquired				15.00%
Ownership interest acquired, step acquisition				40.00%
Noble Midstream Partners LP | Colorado River DevCo
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest acquired				20.00%
Noble Midstream Partners LP | Blanco River and Colorado River DevCos
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration transferred				$ 270,000,000
Noble Midstream Partners LP | Advantage Pipeline
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration transferred					$ 133,000,000
Ownership percentage					50.00%
Length of pipeline | mi					70
Shipping capacity per day (bbls/day) | bbl / d					150
Storage capacity (bbls) | bbl					490
Noble Midstream Partners LP | Black Diamond Gathering LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest											54.40%
Subsequent Event | Southwest Royalties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses							$ 60,000,000
Subsequent Event | CONE Gathering LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses							$ 308,000,000
Subsequent Event | Gulf of Mexico
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total consideration value														$ 480,000,000
Asset consideration														750,000,000
Obligations divested														$ 230,000,000
Subsequent Event | Noble Midstream Partners LP | Saddle Butte
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Length of pipeline | mi	160
Shipping capacity per day (bbls/day) | bbl / d	300
Storage capacity (bbls) | bbl	210
Gas and oil area acquired | a	141,000
Subsequent Event | Black Diamond Gathering LLC | Saddle Butte
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash paid	$ 638,500,000
Tamar and Dalit Fields | Subsequent Event
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest in equity method investments		25.00%													32.50%
CNX Midstream Partners
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Investment, net book value											$ 70,000,000
Owned (shares) | shares											21,700,000
Ownership											33.50%
Advantage Joint Venture
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payments to acquire interest in joint venture					$ 67,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Producing and Undeveloped Net Acres in the DJ Basin
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales Proceeds												$ 486,000,000
Land sold (acres) | a												33,100
Consideration expected									505,000,000			$ 505,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Bowdoin Property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales Proceeds												152,000,000
Gain (loss) on divestitures												(23,000,000)
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Alon A And Alon C
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total consideration value									73,000,000			73,000,000
Consideration adjustment												6,000,000
Asset consideration									$ 67,000,000			$ 67,000,000
Ownership interest sold									47.00%			47.00%
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Cyprus Block 12
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses								$ 40,000,000				$ 131,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Subsequent Event | Tamar and Dalit Fields
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest sold		7.50%
Proceeds from sale of ownership interest		$ 560,000,000
Shares received in divestiture of interest in equity method investment (in shares) | shares		38,500,000
Disposal Group, Held-for-sale, Not Discontinued Operations | Tamar and Dalit Fields
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Investment, net book value											$ 293,000,000
Leaseholds and Leasehold Improvements | Marcellus Shale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset consideration			$ 883,000,000
Subsidiaries | Blanco River and Colorado River DevCos
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration transferred				270,000,000
Cash paid				$ 245,000,000
Developed gas and oil area | a				111,000
Stock issued (shares) | shares				562,430
Proceeds from issuance of common limited partners units				$ 138,000,000
Proceeds from debt				$ 90,000,000