Consolidated Statements of Operations (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Revenues	$ 4,310	$ 3,877	$ 11,362	$ 10,453
Cost of sales:
Production and delivery	2,802	2,529	7,497	7,984
Depreciation, depletion and amortization	418	643	1,257	1,937
Impairment of oil and gas properties	0	239	0	4,317
Total cost of sales	3,220	3,411	8,754	14,238
Selling, general and administrative expenses	106	110	366	408
Mining exploration and research expenses	27	13	61	46
Environmental obligations and shutdown costs (credits)	73	(3)	81	18
Net gain on sales of assets	(33)	(13)	(66)	(762)
Total costs and expenses	3,393	3,518	9,196	13,948
Operating income (loss)	917	359	2,166	(3,495)
Interest expense, net	(304)	(187)	(633)	(574)
Net loss (gain) on exchanges and early extinguishment of debt	11	15	8	51
Other income (expense), net	2	(10)	36	54
Income (loss) from continuing operations before income taxes and equity in affiliated companies’ net earnings	626	177	1,577	(3,964)
(Provision for) benefit from income taxes	(387)	114	(747)	(79)
Equity in affiliated companies’ net earnings	3	1	6	9
Net income (loss) from continuing operations	242	292	836	(4,034)
Net income (loss) from discontinued operations	3	(6)	50	(191)
Net income (loss)	245	286	886	(4,225)
Net income attributable to noncontrolling interests:
Continuing operations	35	(37)	(106)	(146)
Discontinued operations	0	(22)	(4)	(44)
Preferred dividends attributable to redeemable noncontrolling interest	0	(10)	0	(31)
Net income (loss) attributable to common stockholders	$ 280	$ 217	$ 776	$ (4,446)
Basic and diluted net income (loss) per share attributable to common stockholders:
Continuing operations	$ 0.19	$ 0.18	$ 0.50	$ (3.27)
Discontinued operations	0.00	(0.02)	0.03	(0.18)
Basic and diluted net income (loss) per share attributable to common stockholders:	$ 0.19	$ 0.16	$ 0.53	$ (3.45)
Basic	1,448	1,346	1,447	1,289
Diluted	1,454	1,351	1,453	1,289