Basis of Presentation (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Feb. 01, 2016	Dec. 31, 2015
Oil, Gas and NGL Sales		$ 823	$ 732	$ 1,528	$ 1,481
Share Price						$ 31.65
Production Expense
Lease Operating Expense		119	129	281	286
Production and Ad Valorem Taxes		40	28	43	61
Transportation and Gathering Expense (1)	[1]	115	61	222	122
Total		274	218	546	469
Other Operating (Income) Expense, Net
Loss on Asset Due to Terminated Contract	[2]	5	0	47	0
Midstream Gathering and Processing (Income) Expense, Net	[3]	15	12	37	22
Asset Impairments		0	15	0	43
Pension And Other Postretirement Plans, Termination Expense		0	21	0	21
Facility Costs		3	7	5	7
Gain on Extinguishment of Debt	[4]	0	0	(80)	0
Other, Net		(4)	13	12	10
Total		17	85	20	121
Other Non-Operating Expense (Income), Net
Deferred Compensation Expense	[5]	5	(7)	5	(5)
Other Expense (Income), Net		2	(2)	(2)	(4)
Total		7	(9)	3	(9)
Additional expense due to unutilized firm transportation and shortfalls in delivering or transporting minimum volumes under certain commitments		7	5	23	9
Accounts Receivable, Net
Commodity Sales		338		338			$ 298
Joint Interest Billings		19		19			20
Proceeds Receivable	[6]	40		40			0
Severance Tax Refund	[7]	28		28			0
Other		75		75			151
Allowance for Doubtful Accounts		(24)		(24)			(19)
Total		476		476			450
Other Current Assets
Inventories, Materials and Supplies		93		93			92
Inventories, Crude Oil		25		25			23
Assets Held-for-Sale	[8]	18		18			67
Prepaid Expenses and Other Current Assets		48		48			34
Total		184		184			216
Other Noncurrent Assets
Investments in Unconsolidated Subsidiaries		467		467			453
Mutual Fund Investments		79		79			90
Commodity Derivative Assets		0		0			10
Other Assets		47		47			67
Total		593		593			620
Other Current Liabilities
Production and Ad Valorem Taxes		142		142			166
Derivative Liability, Current		35		35			0
Income Taxes Payable		35		35			86
Asset Retirement Obligations		128		128			128
Interest Payable		75		75			83
Current Portion of Capital Lease Obligations		56		56			53
Other		124		124			161
Total		595		595			677
Other Noncurrent Liabilities
Deferred Compensation Liabilities		225		225			217
Asset Retirement Obligations		855		855			861
Accrual for Taxes Other than Income Taxes		21		21			68
Derivative Liability, Noncurrent		31		31			0
Other		41		41			73
Total		$ 1,173		$ 1,173			$ 1,219
Percentage of divestiture farmed out		35.00%		35.00%			35.00%
Gain (Loss) on Disposition of Oil and Gas Property		$ (23)	1	$ (23)	0
Restructuring Charges		0	18	1	18
Finalization of Purchase Price Allocation for Rosetta Merger	[9]	(25)	$ 0	(25)	$ 0
Phantom Units [Member]
Shares issued						1
State and Local Jurisdiction [Member]
Other Non-Operating Expense (Income), Net
Accrual of severance tax refund				28
NGL Revenue Previously Netted with Expense [Member]
Oil, Gas and NGL Sales		$ 10		$ 19

[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 and prior year amounts of $10 million and $19 million for the three and six months ended June 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 8. Capitalized Exploratory Well Costs and Undeveloped Leasehold and Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations - Executive Overview - Exploration Program Update

[3] For the three months and six months ended June 30, 2016, amount includes $7 million and $23 million, respectively, of expense due to unutilized firm transportation and shortfalls in delivering or transporting minimum volumes under certain commitments.For the three months and six months ended June 30, 2015, amount includes $5 million and $9 million, respectively, of expense due to unutilized firm transportation and shortfalls in delivering or transporting minimum volumes under certain commitments.

[4] Amount relates to the tendering of senior notes assumed in the Rosetta Merger. See Note 6. Debt.

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

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

[7] Amount relates to the accrual of a $28 million onshore US severance tax receivable.

[8] Assets held for sale at June 30, 2016 include certain producing and undeveloped crude oil and natural gas interests in the DJ Basin, while assets held for sale at December 31, 2015 include the Karish and Tanin natural gas discoveries, offshore Israel. See Note 4. Divestitures

[9] Amount relates to an adjustment recorded to the purchase price allocation related to the Rosetta Merger. See Note 3. Rosetta Merger.