Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Apr. 30, 2017	Apr. 24, 2017
Tax Credit Carryforward [Line Items]
Deferred tax expense related to GILTI				$ 34
Deferred tax benefit associated with a write-off of foreign exploration losses				50
Operating loss carryforwards			$ 2,700
Foreign loss carryforward	$ 320		327	320
Toll tax accrued	21			21	$ 268
Transition tax for accumulated foreign earnings	261
Income tax expense (benefit)			$ (343)	$ 126	$ (1,141)
Effective Rate			19.30%	90.00%	52.10%
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]
Change in enacted tax rate, amount					$ 107
Foreign tax credits				$ 240	$ 252
Income tax expense (benefit)		$ (145)
Global Intangible Low-Taxed Income
Tax Credit Carryforward [Line Items]
Change in enacted tax rate, amount			$ 14	34
Foreign Loss Carryforward
Tax Credit Carryforward [Line Items]
Foreign loss carryforward	187		192	187
Foreign Tax Credit
Tax Credit Carryforward [Line Items]
Foreign loss carryforward	$ 132		133	$ 132
Domestic Tax Authority
Tax Credit Carryforward [Line Items]
Operating loss carryforwards			2,000
Foreign Tax Authority
Tax Credit Carryforward [Line Items]
Operating loss carryforwards			$ 691
Tamar and Dalit Fields | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Tax Credit Carryforward [Line Items]
Ownership interest sold		7.50%
Israel Tax Authority
Tax Credit Carryforward [Line Items]
Effective Rate			46.80%