Additional Financial Statement Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Production Expense
Lease Operating Expense	$ 563	$ 593	$ 524
Production and Ad Valorem Taxes	127	184	188
Transportation Expense	272	170	132
Total	962	947	844
Other Operating Expense, Net
Midstream Gathering and Processing (Income) Expense, Net	9	11	6
Corporate Restructuring Charges	51	0	0
Stacked Drilling Rig Expense	30	0	0
Pension Plan Expense	88	0	0
Rosetta Merger Expense	81	0	0
(Gain) Loss on Divestitures	0	(73)	(36)
Inventory Adjustment	20	0	0
Other, Net	37	38	43
Total	316	(24)	13
Other Non-Operating (Income) Expense, Net
Deferred Compensation (Income) Expense	(12)	(25)	26
Other (Income) Expense, Net	(3)	(1)	(5)
Total	(15)	(26)	21
Accounts Receivable, Net
Commodity Sales	298	405
Joint Interest Billings	20	297
Other	151	171
Allowance for Doubtful Accounts	(19)	(16)
Total	450	857
Other Current Assets
Inventories, Materials and Supplies	92	81
Inventories, Crude Oil	23	24
Assets Held for Sale	67	180
Prepaid Expenses and Other Assets, Current	34	40
Total	216	325
Other Noncurrent Assets
Equity Method Investments	453	325	$ 437
Mutual Fund Investments	90	111
Commodity Derivative Assets, Noncurrent	10	180
Other Assets, Noncurrent	67	64
Total	620	680
Other Current Liabilities
Production and Ad Valorem Taxes	166	110
Income Taxes Payable	86	180
Deferred Income Taxes, Current	0	158
Asset Retirement Obligations, Current	128	81
Accrued Benefit Costs, Current	3	125
Interest Payable	83	70
Current Portion of Capital Lease and Other Obligations	53	68
Other Liabilities, Current	158	152
Total	677	944
Other Noncurrent Liabilities
Deferred Compensation Liabilities, Noncurrent	217	218
Asset Retirement Obligations, Noncurrent	861	670
Accrued Benefit Costs, Noncurrent	25	24
Other Liabilities, Noncurrent	116	175
Total	$ 1,219	$ 1,087