Consolidated Statements of Operations (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Revenues	$ 3,546	$ 5,168	$ 7,338	$ 10,036
Cost of sales:
Production and delivery	3,002	2,915	5,978	5,723
Depreciation, depletion and amortization	352	442	699	893
Metals inventory adjustments	2		59	2
Total cost of sales	3,354	3,357	6,677	6,616
Selling, general and administrative expenses	97	109	209	240
Mining exploration and research expenses	31	24	58	45
Environmental obligations and shutdown costs	23	59	65	68
Net loss (gain) on sales of assets	8	(45)	(25)	(56)
Total costs and expenses	3,513	3,504	6,984	6,913
Operating income	33	1,664	354	3,123
Interest expense, net	(132)	(142)	(278)	(293)
Net gain (loss) on early extinguishment of debt	0	9	(6)	8
Other income, net	5	20	19	49
(Loss) income from continuing operations before income taxes and equity in affiliated companies’ net earnings	(94)	1,551	89	2,887
Benefit from (provision for) income taxes	15	(515)	(90)	(1,021)
Equity in affiliated companies’ net earnings	5	3	2	1
Net (loss) income from continuing operations	(74)	1,039	1	1,867
Net (loss) income from discontinued operations	0	(4)	1	(15)
Net income	(74)	1,035	2	1,852
Net (income) loss attributable to noncontrolling interests:
Continuing operations	2	(166)	(43)	(291)
Net (loss) income attributable to common stockholders	$ (72)	$ 869	$ (41)	$ 1,561
Earnings Per Share, Basic and Diluted [Abstract]
Continuing operations (in dollars per share)	$ (0.05)	$ 0.60	$ (0.03)	$ 1.08
Discontinued operations (in dollars per share)	0	0	0	(0.01)
Earnings per share, basic (in dollars per share)	(0.05)	0.60	(0.03)	1.07
Continuing operations (in dollars per share)	(0.05)	0.59	(0.03)	1.08
Discontinued operations (in dollars per share)	0	0	0	(0.01)
Earnings per share, diluted (in dollars per share)	$ (0.05)	$ 0.59	$ (0.03)	$ 1.07
Basic weighted-average shares of common stock outstanding	1,451	1,449	1,451	1,449
Diluted weighted-average shares of common shares outstanding	1,451	1,458	1,451	1,458
Dividends declared per share of common stock (in dollars per share)	$ 0.05	$ 0.05	$ 0.10	$ 0.10