Accounting for Suspended Exploratory Wells (Details Textual) $ in Millions		12 Months Ended
		Dec. 31, 2015 USD ($) Well Project	Dec. 31, 2014 USD ($) Project	Dec. 31, 2013 USD ($) Project
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized exploratory well costs that have been capitalized for period greater than one year | $		$ 2,823	$ 2,673	$ 2,604
Number of projects with exploratory well costs that have been capitalized for a period greater than one year | Project	[1]	39	51	51
Expected period for decision on the recognition of proved reserves		5 years
Capitalized exploratory well costs that have been capitalized for period greater than one year, number of wells | Well		165
Drilling Activity [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized exploratory well costs that have been capitalized for period greater than one year | $		$ 1,662
Number of projects with exploratory well costs that have been capitalized for a period greater than one year | Project		20
No Drilling Activity [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized exploratory well costs that have been capitalized for period greater than one year | $		$ 1,161
Number of projects with exploratory well costs that have been capitalized for a period greater than one year | Project		19
Undergoing Front End Engineering and Design with Final Investment Decision Expected [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized exploratory well costs that have been capitalized for period greater than one year | $		$ 190
Number of projects with exploratory well costs that have been capitalized for a period greater than one year | Project		2
Undergoing front-end engineering and design with final investment decision expected in three years		4 years
Development Concept Under Review by Government [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized exploratory well costs that have been capitalized for period greater than one year | $		$ 99
Number of projects with exploratory well costs that have been capitalized for a period greater than one year | Project		1
Reviewing Development Alternatives [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized exploratory well costs that have been capitalized for period greater than one year | $		$ 814
Number of projects with exploratory well costs that have been capitalized for a period greater than one year | Project		7
Miscellaneous Activities for Projects with Smaller Amounts Suspended [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Number of projects with exploratory well costs that have been capitalized for a period greater than one year | Project		9
Capitalized exploratory well costs that are approved and construction in progress | $		$ 58

[1] Certain projects have multiple wells or fields or both.