Derivatives (Details 2) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Gross and net fair values of outstanding derivatives (in millions)
Collateral received netted against derivative assets	$ 1	$ 0
Collateral paid netted against derivative liabilities	17	8
Collateral deposited with clearinghouses and brokers	35	44
Credit risk contingent features
Net derivative liabilities with credit-risk-contingent features	0	4
Amount of collateral posted	0	3
Cash-flow hedges | Other current assets
Gross and net fair values of outstanding derivatives (in millions)
Total net fair value, asset	3
Cash-flow hedges | Other assets
Gross and net fair values of outstanding derivatives (in millions)
Total net fair value, asset	3
Not designated as hedging instruments
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		756
Less: counterparty netting and cash collateral, asset	(223)	(742)
Less: counterparty netting and cash collateral, liability	(240)
Total net fair value, asset	63	97
Total net fair value, liability	304	240
Not designated as hedging instruments | Other current assets
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross	274	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	9	11
Not designated as hedging instruments | Accrued liabilities
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross	309	886
Not designated as hedging instruments | Other Liabilities
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		996
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	235	110
Not designated as hedging instruments | Other assets
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		839
Total net fair value, asset	283
Total net fair value, liability	544
Not designated as hedging instruments | Commodity Contracts
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross	286	839
Commodity contract derivative liability, gross	$ 544	$ 996