Suspended Wells - Aging of suspended well balances (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013 numberofprojects		Dec. 31, 2012 numberofprojects		Dec. 31, 2011 numberofprojects	Dec. 31, 2010
Aging of suspended well cost
Exploratory well costs capitalized for a period of one year or less	$ 437		$ 186		$ 115
Exploratory well costs capitalized for a period greater than one year	557		852		922
Ending balance	$ 994	[1]	$ 1,038	[2]	$ 1,037	$ 1,013
Number of projects that have exploratory well costs that have been capitalized for a period greater than one year	29		35		40

[1]    *Includes $57 million of assets held for sale in Nigeria.

[2] **Includes $190 million of assets held for sale—$133 million in Kazakhstan and $57 million in Nigeria.