Segment Information (Details) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2015 USD ($) Operating_Segments	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Segment Reporting Information [Line Items]
Number of Operating Segments | Operating_Segments			4
Oil and Gas Sales Revenue			$ 3,043	$ 4,931	$ 4,809
Income from Equity Method Investees			90	170	206
Revenues			3,133	5,101	5,015
DD&A			2,131	1,759	1,568
Asset Impairments	$ 5	$ 31	533	500	86
Goodwill Impairment			779	0	0
(Gain) Loss on Divestitures			0	(73)	(36)
Cash (Received) Paid in Settlement of Commodity Derivative Instruments			(501)	(976)	133
Income (Loss) from Continuing Operations Before Income Taxes			(2,219)	1,710	1,344
Equity Method Investments	453		453	325	437
Additions to Long-Lived Assets			3,062	5,152	4,534
Goodwill at End of Year (2)	0		0	620	627
Total Assets at End of Year	24,196		24,196	22,518	19,598
Foreign Countries
Segment Reporting Information [Line Items]
Other Revenue, Net			1,100	1,800	1,800
Total Assets at End of Year	3,900		3,900	4,400		$ 4,500
United States
Segment Reporting Information [Line Items]
Oil and Gas Sales Revenue			1,961	3,175	3,004
Income from Equity Method Investees			51	9	0
Revenues			2,012	3,184	3,004
DD&A			1,692	1,318	1,117
Asset Impairments			158	392	39
Goodwill Impairment			779
(Gain) Loss on Divestitures				(34)	(36)
Cash (Received) Paid in Settlement of Commodity Derivative Instruments			(347)	(604)	67
Income (Loss) from Continuing Operations Before Income Taxes			(1,553)	1,150	790
Equity Method Investments	226		226	82	184
Additions to Long-Lived Assets			2,534	4,389	3,475
Goodwill at End of Year (2)	0		0	620	627
Total Assets at End of Year	18,831		18,831	16,365	13,094
West Africa
Segment Reporting Information [Line Items]
Oil and Gas Sales Revenue			580	1,177	1,252
Income from Equity Method Investees			39	161	206
Revenues			619	1,338	1,458
DD&A			326	299	261
Asset Impairments			339	0	0
Goodwill Impairment			0
(Gain) Loss on Divestitures				0	0
Cash (Received) Paid in Settlement of Commodity Derivative Instruments			(154)	(372)	66
Income (Loss) from Continuing Operations Before Income Taxes			(77)	1,222	936
Equity Method Investments	227		227	223	234
Additions to Long-Lived Assets			124	261	453
Goodwill at End of Year (2)	0		0	0	0
Total Assets at End of Year	2,299		2,299	2,763	3,199
Eastern Mediterranean
Segment Reporting Information [Line Items]
Oil and Gas Sales Revenue			497	479	391
Income from Equity Method Investees			0	0	0
Revenues			497	479	391
DD&A			70	63	97
Asset Impairments			36	14	47
Goodwill Impairment			0
(Gain) Loss on Divestitures				0	0
Cash (Received) Paid in Settlement of Commodity Derivative Instruments			0	0	0
Income (Loss) from Continuing Operations Before Income Taxes			306	284	162
Equity Method Investments	0		0	0	0
Additions to Long-Lived Assets			147	201	420
Goodwill at End of Year (2)	0		0	0	0
Total Assets at End of Year	2,677		2,677	2,806	2,753
Other Int'l & Corporate
Segment Reporting Information [Line Items]
Oil and Gas Sales Revenue			5	100	162
Income from Equity Method Investees			0	0	0
Revenues			5	100	162
DD&A			43	79	93
Asset Impairments			0	94	0
Goodwill Impairment			0
(Gain) Loss on Divestitures				(39)	0
Cash (Received) Paid in Settlement of Commodity Derivative Instruments			0	0	0
Income (Loss) from Continuing Operations Before Income Taxes			(895)	(946)	(544)
Equity Method Investments	0		0	20	19
Additions to Long-Lived Assets			257	301	186
Goodwill at End of Year (2)	0		0	0	0
Total Assets at End of Year	$ 389		$ 389	$ 584	$ 552