Basis of Presentation (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended		6 Months Ended		12 Months Ended
		Mar. 03, 2015	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost (Credit) Arising During Period, before Tax					$ 61
Common stock, par value per share (in dollars per share)			$ 0.01		$ 0.01		$ 0.01
Proceeds from Issuance of Shares of Common Stock to Public, Net of Offering Costs				$ 0	$ 1,112
Repayment of outstanding indebtedness					$ 150
Common stock, shares authorized (in shares)			1,000,000,000		1,000,000,000		500,000,000
Debt Issuance Cost			$ 47				$ 50
Production Expense
Lease Operating Expense			129	150	$ 286	$ 292
Production and Ad Valorem Taxes			28	53	61	102
Transportation and Gathering Expense			56	41	112	80
Total			213	244	459	474
Other Operating Expense Net [Abstract]
Midstream Gathering and Processing Expense			6	4	10	7
Corporate Restructuring Expense	[1]		18	0	18	0
Stacked Drilling Rig Expense	[2]		7	0	7	0
Pension Plan Termination Expense	[3]		21	0	21	0
Other, Net			(16)	(17)	(17)	(23)
Total			67	(23)	73	(12)
Other Non-Operating (Income) Expense, Net
Deferred Compensation Expense	[4]		(7)	8	(5)	12
Other (Income) Expense, Net			(2)	0	(4)	1
Total			(9)	$ 8	(9)	$ 13
Accounts Receivable, Net
Commodity Sales			296		296		405
Joint Interest Billings			175		175		297
Other			102		102		171
Allowance for Doubtful Accounts			(19)		(19)		(16)
Total			554		554		857
Other Current Assets
Inventories, Materials and Supplies			79		79		81
Inventories, Crude Oil			20		20		24
Assets Held-for-Sale	[5]		77		77		180
Prepaid Expenses and Other Current Assets			68		68		40
Total			244		244		325
Other Noncurrent Assets
Investments in Unconsolidated Subsidiaries			400		400		325
Mutual Fund Investments			112		112		111
Commodity Derivative Assets			100		100		180
Other Assets			102		102		99
Total			714		714		715
Other Current Liabilities
Production and Ad Valorem Taxes			151		151		110
Income Taxes Payable			117		117		180
Deferred Income Taxes, Current			91		91		158
Accrued Benefit Costs, Current			111		111		125
Asset Retirement Obligations			135		135		81
Interest Payable			69		69		70
Current Portion of Capital Lease Obligations			61		61		68
Other			99		99		152
Total			834		834		944
Other Noncurrent Liabilities
Deferred Compensation Liabilities			218		218		218
Asset Retirement Obligations			717		717		670
Accrued Benefit Costs			19		19		24
Other			76		76		175
Total			$ 1,030		$ 1,030		$ 1,087
Common Stock Authorized prior to Certificate of Incorporation Amendment [Member]
Common stock, shares authorized (in shares)			500,000,000		500,000,000
Common Stock Authorized after Stock Issuance [Member]
Common stock, shares authorized (in shares)			1,000,000,000		1,000,000,000
Underwritten Public Offering [Member]
Underwritten public offering (in shares)		21,000,000
Common stock, par value per share (in dollars per share)		$ 0.01
Sale of stock (in dollars per share)		$ 47.5
Over-Allotment Option [Member]
Underwritten public offering (in shares)		3,150,000
Common stock, par value per share (in dollars per share)		$ 0.01

[1] Amount represents severance costs and expenses associated with the relocation of our accounting department from Ardmore, Oklahoma to Houston, Texas.

[2] Amount represents the day rate cost associated with drilling rigs under contract, but not currently being utilized in our US onshore drilling programs.

[3] Amount includes the reclassification of a portion of the remaining actuarial loss from AOCL, related to our defined benefit pension plan which is in the process of being terminated.

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

[5] (1) Assets held for sale include our Tanin and Karish natural gas discoveries, offshore Israel. See Update on Core Area – Israel, above.