Basis of Presentation (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2016		Sep. 30, 2015		Sep. 30, 2016		Sep. 30, 2015		Jul. 04, 2016	Feb. 01, 2016	Dec. 31, 2015
Oil, Gas and NGL Sales		$ 882		$ 783		$ 2,411		$ 2,264
Share Price											$ 31.65
Production Expense
Lease Operating Expense		131		133		412		419
Production and Ad Valorem Taxes		30		28		73		89
Transportation and Gathering Expense (1)	[1]	113		86		335		207
Total		274		247		820		715
Other Operating (Income) Expense, Net
Loss on Asset Due to Terminated Contract	[2]	(3)		0		44		0
Midstream Gathering and Processing (Income) Expense, Net	[3]	20		10		58		25
Asset Impairments		0		0		0		43
Inventory Write-down		14		0		14		0
Business Exit Costs		4		18		8		18
Business combination costs		0		71		0	[4]	73	[4]
Pension And Other Postretirement Plans, Termination Expense		0		67		0		88
Facility Costs		3		13		8		20
Gain on Extinguishment of Debt	[5]	0		0		(80)		0
Other, Net		7		(12)		16		4
Total		45		188		66		310
Other Non-Operating Expense (Income), Net
Deferred Compensation Expense	[6]	2		(13)		7		(19)
Other (Income) Expense, Net		(3)		1		(4)		(1)
Total		(1)		(12)		3		(20)
Additional expense due to unutilized firm transportation and shortfalls in delivering or transporting minimum volumes under certain commitments		12		6		39		15
Accounts Receivable, Net
Commodity Sales		317				317						$ 298
Joint Interest Billings		66				66						20
Proceeds Receivable	[7]	40				40						0
Other		86				86						151
Allowance for Doubtful Accounts		(23)				(23)						(19)
Total		486				486						450
Other Current Assets
Inventories, Materials and Supplies		75				75						92
Inventories, Crude Oil		25				25						23
Assets Held-for-Sale	[8]	214				214						67
Prepaid Expenses and Other Current Assets		38				38						34
Total		352				352						216
Other Noncurrent Assets
Investments in Unconsolidated Subsidiaries		460				460						453
Mutual Fund Investments		83				83						90
Commodity Derivative Assets		0				0						10
Other Assets		44				44						67
Total		587				587						620
Other Current Liabilities
Production and Ad Valorem Taxes		121				121						166
Derivative Liability, Current		27				27						0
Income Taxes Payable		168				168						86
Asset Retirement Obligations		128				128						128
Interest Payable		93				93						83
Current Portion of Capital Lease Obligations		61				61						53
Other		144				144						161
Total		742				742						677
Other Noncurrent Liabilities
Deferred Compensation Liabilities		232				232						217
Asset Retirement Obligations		820				820						861
Accrual for Taxes Other than Income Taxes		35				35						68
Derivative Liability, Noncurrent		8				8						0
Other		44				44						73
Total		$ 1,139				$ 1,139						$ 1,219
Percentage of divestiture farmed out		35.00%				35.00%						35.00%
Gain (Loss) on Disposition of Oil and Gas Property		$ 0		0		$ (23)		0
Restructuring Charges		0		21		0		39
Finalization of Purchase Price Allocation for Rosetta Merger		0	[4]	$ 0	[4]	(25)		$ 0	[4]
Phantom Units [Member]
Shares issued											1
NGL Revenue Previously Netted with Expense [Member]
Oil, Gas and NGL Sales		18				37
Tamar Field, Offshore Israel [Member]
Other Current Assets
Assets Held-for-Sale	[8]	$ 127				$ 127
Other Noncurrent Liabilities
Percentage of divestiture farmed out										3.00%
Working interest		3.00%				3.00%

[1] Certain of our revenue received from purchasers was historically presented with deductions for transportation, gathering, fractionation or processing costs. Beginning in 2016, we have changed our presentation of revenue to no longer include these expenses as deductions from revenue. These costs are now included within production expense. Prior year amounts of $18 million and $37 million for the three and nine months ended September 30, 2015 have been reclassified to conform to the current presentation.

[2] Amount relates to the termination of a rig contract offshore Falkland Islands as a result of a supplier's non-performance. See Note 9. Capitalized Exploratory Well Costs and Undeveloped Leasehold Costs and Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations - Executive Overview - Exploration Program Update

[3] For the three and nine months ended September 30, 2016, amount includes $12 million and $39 million, respectively, of expense due to unutilized firm transportation and shortfalls in delivering or transporting minimum volumes under certain commitments.Prior year amounts of $6 million and $15 million for the three and nine months ended September 30, 2015, were previously presented within production expense. These amounts have been reclassified to conform to the current presentation.

[4] Amount relates to an adjustment recorded to the purchase price allocation related to the Rosetta Merger. See Note 5. Rosetta Merger.

[5] Amount relates to the tendering of senior notes assumed in the Rosetta Merger. See Note 7. Debt.

[6] Amounts represent decreases (increases) in the fair value of shares of our common stock held in a rabbi trust.

[7] Amount relates to proceeds to be received from our farm-out of 35% interest in Block 12 offshore Cyprus. See Note 4. Divestitures.

[8] Assets held for sale at September 30, 2016 primarily include $127 million relating to our 3% working interest in the Tamar project, offshore Israel, and certain producing and undeveloped assets in the DJ Basin and Eagle Ford Shale, onshore US. Assets held for sale at December 31, 2015 include the Karish and Tanin natural gas discoveries, offshore Israel. See Note 4. Divestitures