Income Taxes - Reconciliation of Tax Computed at the U.S. Federal Statutory Rate to Income Tax Expense (Benefit) Table (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income (loss) before income taxes
Domestic	$ (1,322)	$ (3,728)	$ (9,155)
Foreign	(366)	(101)	(534)
Income (Loss) Before Income Taxes	$ (1,688)	$ (3,829)	$ (9,689)
U.S. federal statutory tax rate	35.00%	35.00%	35.00%
Tax computed at the U.S. federal statutory rate	$ (591)	$ (1,340)	$ (3,391)
(Income) loss attributable to noncontrolling interests	(85)	(92)	42
Adjustments resulting from
State income taxes (net of federal income tax benefit)	25	(108)	(81)
U.S. federal tax reform	(1,168)	0	0
Tax impact from foreign operations	166	80	299
Non-deductible Algerian exceptional profits tax	110	106	102
Net changes in uncertain tax positions	90	90	54
Dispositions of non-deductible goodwill	6	205	62
Other, net	(30)	38	36
Total income tax expense (benefit)	$ (1,477)	$ (1,021)	$ (2,877)
Effective tax rate	88.00%	27.00%	30.00%