CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues and Other
Oil sales		$ 6,552	$ 4,668	$ 5,420
Natural-gas sales		1,348	1,564	2,007
Natural-gas liquids sales		1,069	921	833
Gathering, processing, and marketing sales		2,000	1,294	1,226
Gains (losses) on divestitures and other, net		939	(578)	(788)
Total		11,908	7,869	8,698
Costs and Expenses
Oil and gas operating		1,000	811	1,014
Oil and gas transportation		914	1,002	1,117
Exploration		2,541	946	2,644
Gathering, processing, and marketing		1,560	1,087	1,054
General and administrative		1,075	1,440	1,176
Depreciation, depletion, and amortization		4,279	4,301	4,603
Production, property, and other taxes		582	536	553
Impairments		408	227	5,075
Other operating expense		221	118	271
Total		12,580	10,468	17,507
Operating Income (Loss)		(672)	(2,599)	(8,809)
Other (Income) Expense
Interest expense		932	890	825
Loss on early extinguishment of debt		2	155	0
(Gains) losses on derivatives, net		131	292	(100)
Other (income) expense, net		(53)	(101)	154
Total		1,016	1,230	880
Income (Loss) Before Income Taxes		(1,688)	(3,829)	(9,689)
Income tax expense (benefit)		(1,477)	(1,021)	(2,877)
Net Income (Loss)		(211)	(2,808)	(6,812)
Net income (loss) attributable to noncontrolling interests	[1]	245	263	(120)
Net Income (Loss) Attributable to Common Stockholders		$ (456)	$ (3,071)	$ (6,692)
Per Common Share
Net income (loss) attributable to common stockholders—basic (in usd per share)		$ (0.85)	$ (5.90)	$ (13.18)
Net income (loss) attributable to common stockholders—diluted (in usd per share)		$ (0.85)	$ (5.90)	$ (13.18)
Average Number of Common Shares Outstanding—Basic		548	522	508
Average Number of Common Shares Outstanding—Diluted		548	522	508
Dividends (per Common Share) (in usd per share)		$ 0.20	$ 0.20	$ 1.08
Commodity Contract and Interest-Rate Swap [Member]
Other (Income) Expense
(Gains) losses on derivatives, net		$ 135	$ 286	$ (99)

[1] Presentation has been adjusted to align with the current analysis of segment performance. Net income (loss) attributable to noncontrolling interests, previously reported within the Midstream segment, is now presented within Other and Intersegment Eliminations. Other revenues, previously reported within Other and Intersegment Eliminations, is now presented within the applicable segments.