Capitalized Exploratory Well Costs and Undeveloped Leasehold Costs - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Undeveloped leasehold costs, net	$ 2,373	$ 2,922	$ 2,197
International
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized undeveloped leasehold cost	53
Domestic
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized undeveloped leasehold cost	31
Delaware Basin
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized undeveloped leasehold cost	2,200
Eagle Ford
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized undeveloped leasehold cost	$ 100