CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	1 Months Ended	3 Months Ended									12 Months Ended
	Feb. 29, 2012	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Revenues		$ 5,041	$ 4,310	$ 3,711	$ 3,341	$ 4,377	$ 3,877	$ 3,334	$ 3,242		$ 16,403	$ 14,830	$ 14,607
Cost of sales:
Production and delivery											10,300	10,697	10,693
Depreciation, depletion and amortization											1,714	2,530	3,240
Impairment of Oil and Gas Properties							200	300	3,800		0	4,317	13,144
Metals inventory adjustments											8	36	338
Total cost of sales											12,022	17,580	27,415
Selling, general and administrative expenses											484	607	558
Mining exploration and research expenses											94	64	107
Environmental obligations and shutdown costs											251	20	78
Net gain on sales of assets		(15)	(33)	(10)	(23)	113	(13)	(749)			(81)	(649)	(39)
Total costs and expenses											12,770	17,622	28,119
Operating income (loss)		1,467	917	669	580	703	359	18	(3,872)		3,633	(2,792)	(13,512)
Interest expense, net											(801)	(755)	(617)
Net gain on early extinguishment and exchanges of debt											21	26	0
Other income, net											49	49	1
Income (loss) from continuing operations before income taxes and equity in affiliated companies' net earnings (losses)											2,902	(3,472)	(14,128)
(Provision for) benefit from income taxes											(883)	(371)	1,951
Equity in affiliated companies’ net earnings (losses)											10	11	(3)
Net income (loss) from continuing operations		1,193	242	326	268	202	292	(229)	(4,097)		2,029	(3,832)	(12,180)
Net income (loss) from discontinued operations		16	3	9	38	(2)	(6)	(181)	(4)		66	(193)	91
Net income (loss)		1,209	245	335	306	200	286	(410)	(4,101)		2,095	(4,025)	(12,089)
Net income attributable to noncontrolling interests: Continuing Operations											(274)	(227)	(27)
Net income attributable to noncontrolling interests: Discontinued Operations		0	0	(1)	(3)	(19)	(22)	(12)	(10)		(4)	(63)	(79)
Gain on redemption and preferred dividends attributable to redeemable noncontrolling interest											0	161	(41)
Net income (loss) attributable to common stockholders		$ 1,041	$ 280	$ 268	$ 228	$ 292	$ 217	$ (479)	$ (4,184)		$ 1,817	$ (4,154)	$ (12,236)
Basic and diluted net income (loss) per share attributable to common stockholders:
Continuing operations (in dollars per share)						$ 0.22	$ 0.18	$ (0.23)	$ (3.34)		$ 1.21	$ (2.96)	$ (11.32)
Discontinued operations (in dollars per share)		$ 0.01	$ 0.00	$ 0.00	$ 0.03	(0.01)	(0.02)	(0.15)	(0.01)		0.04	(0.20)	0.01
Earnings per share, basic and diluted (in dollars per share)						$ 0.21	$ 0.16	$ (0.38)	$ (3.35)		$ 1.25	$ (3.16)	$ (11.31)
Weighted Average Number of Shares Outstanding, Basic		1,448,000,000	1,448,000,000	1,447,000,000	1,446,000,000	1,403,000,000	1,346,000,000	1,269,000,000	1,251,000,000		1,447,000,000	1,318,000,000	1,082,000,000
Weighted Average Number of Shares Outstanding, Diluted		1,455,000,000.00	1,454,000,000.00	1,453,000,000.00	1,454,000,000.00	1,410,000,000	1,351,000,000	1,269,000,000	1,251,000,000		1,454,000,000.00	1,318,000,000	1,082,000,000
Dividends declared per share of common stock (in dollars per share)	$ 1.25									$ 0.20	$ 0	$ 0	$ 0.2605