Accounting for Suspended Exploratory Wells (Details Textual) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) Well Project	Dec. 31, 2015 USD ($) Project	Dec. 31, 2014 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 | $	$ 3,095	$ 2,823	$ 2,673
Number of projects with exploratory well costs that have been capitalized for a period greater than one year (in projects) | Project	35	39	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	160
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 | $	$ 1,939
Number of projects with exploratory well costs that have been capitalized for a period greater than one year (in projects) | Project	15
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 | $	$ 1,156
Number of projects with exploratory well costs that have been capitalized for a period greater than one year (in projects) | Project	20
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 (in projects) | 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 | $	$ 107
Number of projects with exploratory well costs that have been capitalized for a period greater than one year (in projects) | Project	2
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 | $	$ 816
Number of projects with exploratory well costs that have been capitalized for a period greater than one year (in projects) | 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 (in projects) | Project	9
Capitalized exploratory well costs that are approved and construction in progress | $	$ 43