Accounting for Suspended Exploratory Wells (Details 1) $ in Millions		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
Capitalized exploratory well costs that have been capitalized for period greater than one year, number of wells | Well		165
Number of projects | Project	[1]	39	51	51
1998–2004 [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		$ 285
Capitalized exploratory well costs that have been capitalized for period greater than one year, number of wells | Well		26
2005–2009 [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		$ 395
Capitalized exploratory well costs that have been capitalized for period greater than one year, number of wells | Well		33
2010–2014 [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		$ 2,143
Capitalized exploratory well costs that have been capitalized for period greater than one year, number of wells | Well		106
2003-2007 [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		$ 200
Number of projects | Project		4
2008–2011 [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		$ 393
Number of projects | Project		6
2012–2015 [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		$ 2,230
Number of projects | Project		29

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