Industry Segments (Details) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) segment	Sep. 30, 2014 USD ($)
Industry Segments
Number of operating segments | segment				3
Segment Information
Net sales		$ 3,116	$ 4,904	$ 9,674	$ 15,005
Pretax operating profit (loss)		(3,051)	1,697	(2,781)	5,598
Income taxes		445	(699)	140	(2,302)
Discontinued operations, net		(3)	213	(10)	741
Less: Net income attributable to noncontrolling interest			(3)		(8)
Net income (loss) attributable to common stock		(2,609)	1,208	(2,651)	4,029
Impairment charges		3,100
Williston Operations
Segment Information
Impairment charges	$ 763
Oil and Gas
Segment Information
Net sales				6,405	10,891
Pretax operating profit (loss)				(3,039)	5,054
Net income (loss) attributable to common stock				(3,039)	5,054
Oil and Gas | Williston Operations
Segment Information
Impairment charges	$ 756
Oil and Gas | Domestic gas operations
Segment Information
Impairment charges				924
Oil and Gas | Libya operations
Segment Information
Impairment charges				676
Oil and Gas | South Texas Eagle Ford non-operated properties
Segment Information
Impairment charges				195
Oil and Gas | Yemen
Segment Information
Impairment charges				41
Oil and Gas | Iraq Operations
Segment Information
Impairment charges				760
Chemical
Segment Information
Net sales				3,038	3,694
Pretax operating profit (loss)				547	409
Net income (loss) attributable to common stock				547	409
Gain on sale of idled site				98
Midstream and Marketing
Segment Information
Net sales				722	1,041
Pretax operating profit (loss)				96	483
Less: Net income attributable to noncontrolling interest					(8)
Net income (loss) attributable to common stock				96	475
Operating segments | Oil and Gas
Segment Information
Net sales		2,054	3,586
Pretax operating profit (loss)		(3,128)	1,568
Net income (loss) attributable to common stock		(3,128)	1,568
Operating segments | Chemical
Segment Information
Net sales		1,008	1,232
Pretax operating profit (loss)		272	140
Net income (loss) attributable to common stock		272	140
Operating segments | Midstream and Marketing
Segment Information
Net sales		231	261
Pretax operating profit (loss)		24	108
Less: Net income attributable to noncontrolling interest			(3)
Net income (loss) attributable to common stock		24	105
Corporate and Eliminations
Segment Information
Net sales		(177)	(175)	(491)	(621)
Pretax operating profit (loss)		(219)	(119)	(385)	(348)
Income taxes		445	(699)	140	(2,302)
Discontinued operations, net		(3)	213	(10)	741
Net income (loss) attributable to common stock		$ 223	$ (605)	$ (255)	$ (1,909)