Revenue from Contracts with Customers - Impact on Financial Statements (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Revenues
Gathering, processing, and marketing sales	$ 360	$ 444
Gains (losses) on divestitures and other, net	19	869
Expenses
Gathering, processing, and marketing	237	350
Income tax expense (benefit)	126	97
Net income (loss) attributable to noncontrolling interests	53	43
Net income (loss) attributable to common stockholders	121	$ (318)
Assets
Net properties and equipment	27,758		$ 27,451
Other Assets	2,134		2,211
Liabilities
Other current liabilities	1,437		1,310
Deferred income taxes	2,267		2,234
Other	4,166		4,109
Equity
Total equity	11,756		$ 13,790
Accounting Standards Update 2014-09 [Member] | Without Adoption of Topic 606 [Member]
Revenues
Gathering, processing, and marketing sales	577
Gains (losses) on divestitures and other, net	21
Expenses
Gathering, processing, and marketing	451
Income tax expense (benefit)	127
Net income (loss) attributable to noncontrolling interests	54
Net income (loss) attributable to common stockholders	124
Assets
Net properties and equipment	27,715
Other Assets	2,122
Liabilities
Other current liabilities	1,434
Deferred income taxes	2,274
Other	4,056
Equity
Total equity	11,807
Accounting Standards Update 2014-09 [Member] | Effect of Change Increase/ (Decrease) [Member]
Revenues
Gathering, processing, and marketing sales	(217)
Gains (losses) on divestitures and other, net	(2)
Expenses
Gathering, processing, and marketing	(214)
Income tax expense (benefit)	(1)
Net income (loss) attributable to noncontrolling interests	(1)
Net income (loss) attributable to common stockholders	(3)
Assets
Net properties and equipment	43
Other Assets	12
Liabilities
Other current liabilities	3
Deferred income taxes	(7)
Other	110
Equity
Total equity	$ (51)