Basis of Presentation (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) MMBoe	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) MMBoe	Jun. 30, 2016 USD ($)	Apr. 24, 2017 USD ($)	Dec. 31, 2016 USD ($)
Goodwill	$ 1,289		$ 1,289			$ 0
Proved undeveloped reserves (MMBOEs) | MMBoe	(551)		(551)
Production Expense
Lease Operating Expense	$ 124	$ 119	$ 263	$ 281
Production and Ad Valorem Taxes	38	40	83	43
Gathering, Transportation and Processing Expense	121	121	240	232
Total	283	280	586	556
Loss on Sale	2,270	0	2,270	0
Firm Transportation Commitment	33		33			0
Other	11	0	11	0
Total	2,322	0	2,322	0
Other Operating (Income) Expense, Net
Marketing Expense	14	9	33	27
Clayton Williams Acquisition Expenses	90	0	94	0
Gain on Extinguishment of Debt	0	0	0	(80)
Loss on Asset Due to Terminated Contract	0	5	4	47
Other, Net	14	(3)	16	16
Total	118	11	147	10
Accounts Receivable, Net
Commodity Sales	408		408			403
Joint Interest Billings	198		198			106
Proceeds Receivable	0		0			40
Other	112		112			86
Allowance for Doubtful Accounts	(19)		(19)			(20)
Total	699		699			615
Other Current Assets
Inventories, Materials and Supplies	65		65			71
Inventories, Crude Oil	23		23			18
Assets Held for Sale	191		191			18
Restricted Cash	0		0			30
Prepaid Expenses and Other Current Assets	59		59			23
Total	338		338			160
Other Noncurrent Assets
Equity Method Investments	286		286			400
Mutual Fund Investments	67		67			71
Other Assets, Noncurrent	79		79			37
Total	432		432			508
Other Current Liabilities
Production and Ad Valorem Taxes	113		113			115
Commodity Derivative Liabilities	0		0			102
Income Taxes Payable	11		11			53
Asset Retirement Obligations	50		50			160
Interest Payable	75		75			76
Current Portion of Capital Lease Obligations	64		64			63
Other Liabilities, Current	196		196			173
Total	509		509			742
Other Noncurrent Liabilities
Deferred Compensation Liabilities	216		216			218
Asset Retirement Obligations	943		943			775
Production and Ad Valorem Taxes	32		32			47
Other Liabilities, Noncurrent	55		55			63
Total	1,279		1,279			$ 1,103
Percentage of divestiture farmed out						35.00%
Firm transportation liability	$ 41	0	$ 41	0
Leviathan
Proved undeveloped reserves (MMBOEs) | MMBoe	(551)		(551)
Marcellus Shale
Proved undeveloped reserves (MMBOEs) | MMBoe	51		51
Proved developed reserves (MMBOEs) | MMBoe	190		190
Decrease (MMBOEs) | MMBoe	241
Clayton Williams Energy
Goodwill	$ 1,300		$ 1,300		$ 1,289
Proved undeveloped reserves (MMBOEs) | MMBoe	(69)		(69)
Proved developed reserves (MMBOEs) | MMBoe	(17)		(17)
Decrease (MMBOEs) | MMBoe			(86)
Other Operating (Income) Expense, Net
Clayton Williams Acquisition Expenses	$ 26		$ 60
Scenario, Previously Reported
Other Operating (Income) Expense, Net
Marketing Expense	2	$ 6	5	$ 10
Other Current Liabilities
Other Noncurrent Liabilities
Firm transportation liability	$ 8		$ 8