Consolidated Statements of Operations (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Revenues	$ 3,711	$ 3,334	$ 7,052	$ 6,576
Cost of sales:
Production and delivery	2,495	2,956	4,695	5,455
Depreciation, depletion and amortization	450	632	839	1,294
Impairment of oil and gas properties	0	291	0	4,078
Total cost of sales	2,945	3,879	5,534	10,827
Selling, general and administrative expenses	107	160	260	298
Mining exploration and research expenses	19	15	34	33
Environmental obligations and shutdown costs	(19)	11	8	21
Net gain on sales of assets	(10)	(749)	(33)	(749)
Total costs and expenses	3,042	3,316	5,803	10,430
Operating income (loss)	669	18	1,249	(3,854)
Interest expense, net	(162)	(196)	(329)	(387)
Net loss (gain) on exchanges and early extinguishment of debt	(4)	39	(3)	36
Other income, net	10	25	34	64
Income (loss) from continuing operations before income taxes and equity in affiliated companies’ net (losses) earnings	513	(114)	951	(4,141)
Provision for income taxes	(186)	(116)	(360)	(193)
Equity in affiliated companies’ net (losses) earnings	(1)	1	3	8
Net income (loss) from continuing operations	326	(229)	594	(4,326)
Net income (loss) from discontinued operations	9	(181)	47	(185)
Net income (loss)	335	(410)	641	(4,511)
Net income attributable to noncontrolling interests:
Continuing operations	(66)	(47)	(141)	(109)
Discontinued operations	(1)	(12)	(4)	(22)
Preferred dividends attributable to redeemable noncontrolling interest	0	(10)	0	(21)
Net income (loss) attributable to common stockholders	$ 268	$ (479)	$ 496	$ (4,663)
Basic and diluted net income (loss) per share attributable to common stockholders:
Continuing operations	$ 0.18	$ (0.23)	$ 0.31	$ (3.54)
Discontinued operations	0.00	(0.15)	0.03	(0.16)
Basic and diluted net income (loss) per share attributable to common stockholders:	$ 0.18	$ (0.38)	$ 0.34	$ (3.70)
Basic	1,447	1,269	1,447	1,260
Diluted	1,453	1,269	1,453	1,260