Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 14, 2018	Apr. 24, 2017
Tax Credit Carryforward [Line Items]
Deferred tax asset, TCJA		$ 10	$ 500
Additional taxable income, TCJA			767
Foreign tax credits			164
Toll tax accrued	$ 21	21	268
Operating loss carryforwards	2,400	2,400
Foreign loss carryforward	320	$ 320	$ 549
Federal Statutory Rate (in hundredths)		21.00%	35.00%	35.00%
Deferred Income Taxes		$ 70	$ 1,227	$ 984
Ownership interest sold				35.00%
Income Tax Expense (Benefit)		$ 126	$ (1,141)	$ (787)
Transition tax for accumulated foreign earnings	261
Effective Rate		90.00%	52.10%	44.40%
Clayton Williams Energy
Tax Credit Carryforward [Line Items]
Deferred tax liabilities						$ 307
Deferred tax assets						$ 450
One-time Deemed Repatriation
Tax Credit Carryforward [Line Items]
Foreign tax credits		$ 252		$ 240
Change in enacted tax rate, amount	5		$ 107
Income Tax Expense (Benefit)			(145)
Write-Off Of Foreign Exploration Losses
Tax Credit Carryforward [Line Items]
Change in enacted tax rate, amount		50
Global Intangible Low-Taxed Income
Tax Credit Carryforward [Line Items]
Change in enacted tax rate, amount		34
Foreign Loss Carryforward
Tax Credit Carryforward [Line Items]
Foreign loss carryforward	187	187	183
Foreign Tax Credit
Tax Credit Carryforward [Line Items]
Foreign loss carryforward	132	132	$ 366
Domestic Tax Authority
Tax Credit Carryforward [Line Items]
Operating loss carryforwards	1,700	1,700
Foreign Tax Authority
Tax Credit Carryforward [Line Items]
Operating loss carryforwards	$ 670	670
Israel
Tax Credit Carryforward [Line Items]
Deferred Income Taxes		$ 12
Effective Rate		46.80%
Israel | Tax Year 2016
Tax Credit Carryforward [Line Items]
Federal Statutory Rate (in hundredths)		25.00%
Israel | Tax Year 2017
Tax Credit Carryforward [Line Items]
Federal Statutory Rate (in hundredths)		24.00%
Israel | Tax Year 2018
Tax Credit Carryforward [Line Items]
Federal Statutory Rate (in hundredths)		23.00%
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Tamar and Dalit Fields
Tax Credit Carryforward [Line Items]
Ownership interest sold					7.50%