Capitalized Exploratory Well Costs and Undeveloped Leasehold Costs - Aging of Exploratory Well Costs (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	$ 348	$ 510	$ 699
Felicita (Block O)
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	48
Yolanda (Block I)
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	24
YoYo (YoYo Block)
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	52
Leviathan-1 Deep
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	94
Dalit
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	24
Cyprus
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	100
Projects less than $20 million
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	6
Suspended Since 2016 and 2017
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	16
Suspended Since 2016 and 2017 | Felicita (Block O)
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	3
Suspended Since 2016 and 2017 | Yolanda (Block I)
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	2
Suspended Since 2016 and 2017 | YoYo (YoYo Block)
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	(1)
Suspended Since 2016 and 2017 | Leviathan-1 Deep
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	6
Suspended Since 2016 and 2017 | Dalit
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	2
Suspended Since 2016 and 2017 | Cyprus
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	11
Suspended Since 2016 and 2017 | Projects less than $20 million
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	(7)
Suspended Since 2014 and 2015
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	49
Suspended Since 2014 and 2015 | Felicita (Block O)
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	7
Suspended Since 2014 and 2015 | Yolanda (Block I)
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	3
Suspended Since 2014 and 2015 | YoYo (YoYo Block)
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	6
Suspended Since 2014 and 2015 | Leviathan-1 Deep
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	8
Suspended Since 2014 and 2015 | Dalit
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	3
Suspended Since 2014 and 2015 | Cyprus
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	12
Suspended Since 2014 and 2015 | Projects less than $20 million
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	10
Suspended Since 2013 and Prior
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	283
Suspended Since 2013 and Prior | Felicita (Block O)
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	38
Suspended Since 2013 and Prior | Yolanda (Block I)
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	19
Suspended Since 2013 and Prior | YoYo (YoYo Block)
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	47
Suspended Since 2013 and Prior | Leviathan-1 Deep
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	80
Suspended Since 2013 and Prior | Dalit
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	19
Suspended Since 2013 and Prior | Cyprus
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	77
Suspended Since 2013 and Prior | Projects less than $20 million
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	$ 3