Derivatives (Details 2) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Gross and net fair values of outstanding derivatives (in millions)
Collateral received netted against derivative assets	$ 15	$ 0
Collateral paid netted against derivative liabilities	3	8
Collateral deposited with clearinghouses and brokers	7	44
Credit risk contingent features
Net derivative liabilities with credit-risk-contingent features	0	4
Amount of collateral posted	0	3
Not designated as hedging instruments
Gross and net fair values of outstanding derivatives (in millions)
Less: counterparty netting and cash collateral, asset	(139)	(742)
Less: counterparty netting and cash collateral, liability	(127)	(756)
Total net fair value, asset	35	97
Total net fair value, liability	165	240
Not designated as hedging instruments | Other current assets
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross	166	828
Not designated as hedging instruments | Long-term receivables and other assets, net
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross	8	11
Not designated as hedging instruments | Accrued liabilities
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross	159	886
Not designated as hedging instruments | Deferred credits and other liabilities
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross	133	110
Not designated as hedging instruments | Commodity Contracts
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross	174	839
Commodity contract derivative liability, gross	$ 292	$ 996