Additional Financial Statement Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Additional Financial Statement Information [Line Items]
Oil and Gas Sales Revenue	$ 3,389	$ 3,093	$ 4,945
Working interest sold	3.50%
Farm down	35.00%
Production Expense
Lease Operating Expense	$ 542	563	593
Production and Ad Valorem Taxes	78	127	184
Transportation and Gathering Expense (1)	463	289	168
Total	1,083	979	945
Leasehold Impairment and Amortization	148	113	43
Dry Hole Cost	579	266	226
Seismic, Geological and Geophysical	76	34	86
Staff Expense	77	43	72
Other	45	32	71
Exploration Expense	925	488	498
Other Operating (Income) Expense, Net
Marketing Expense	58	33	16
Loss on Terminated Contract	41	0	0
(Gain) Loss on Divestitures	(238)	0	(73)
Corporate Restructuring Charges	8	51	0
Gain on Debt Extinguishment	(80)	0	0
Pension Plan Expense	0	88	0
Rosetta Merger Expense	(25)	81	0
Other, Net	70	96	49
Total	(166)	349	(8)
Other Non-Operating (Income) Expense, Net
Deferred Compensation (Income) Expense	11	(12)	(25)
Other (Income) Expense, Net	(2)	(3)	(1)
Total	9	(15)	(26)
Accounts Receivable, Net
Commodity Sales	403	298
Joint Interest Billings	106	20
Proceeds Receivable	40	0
Other	86	151
Allowance for Doubtful Accounts	(20)	(19)
Total	615	450
Other Current Assets
Inventories, Materials and Supplies	71	92
Inventories, Crude Oil	18	23
Assets Held for Sale	18	67
Restricted Cash	30	0
Prepaid Expenses and Other Assets, Current	23	34
Total	160	216
Other Noncurrent Assets
Equity Method Investments	400	453	325
Mutual Fund Investments	71	90
Other Assets, Noncurrent	37	77
Total	508	620
Other Current Liabilities
Production and Ad Valorem Taxes	115	166
Commodity Derivative Liabilities, Current	102	0
Income Taxes Payable	53	86
Asset Retirement Obligations, Current	160	128
Interest Payable	76	83
Current Portion of Capital Lease and Other Obligations	63	53
Other Liabilities, Current	173	161
Total	742	677
Other Noncurrent Liabilities
Deferred Compensation Liabilities, Noncurrent	218	217
Asset Retirement Obligations, Noncurrent	775	861
Production and Ad Valorem Taxes	47	68
Other Liabilities, Noncurrent	63	73
Total	$ 1,103	1,219
Scenario, Previously Reported | NGL Revenue Previously Netted with Expense
Additional Financial Statement Information [Line Items]
Oil and Gas Sales Revenue		$ 50	$ 14