Exploratory Costs Exploratory Costs (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
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	$ 8	$ 43
Number of projects with exploratory costs that have been suspended for a period greater than one year	3	1
Colorado [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Number of projects with exploratory costs that have been suspended for a period greater than one year	2
Eagle Ford Shale [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Number of projects with exploratory costs that have been suspended for a period greater than one year	1
Nuna [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		$ 43