Derivatives (Details 3) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Gross and net fair values of outstanding derivatives (in millions)
Less: counterparty netting and cash collateral, asset	$ (553)	$ (329)
Less: counterparty netting and cash collateral, liability	(578)	(364)
Total net fair value, asset	33	51
Total net fair value, liability	84	58
Collateral received netted against derivative assets	7	11
Collateral paid netted against derivative liabilities	32	46
Collateral deposited with clearinghouses and brokers	115	103
Credit risk contingent features
Net derivative liabilities with credit-risk-contingent features	6	8
Amount of collateral posted	23	23
Commodity Contracts
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross	586	380
Commodity contract derivative liability, gross	662	422
Cash-flow hedges | Commodity Contracts
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		4
Cash-flow hedges | Commodity Contracts | Accrued liabilities
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		4
Not designated as hedging instruments | Commodity Contracts
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross	586	380
Commodity contract derivative liability, gross	662	418
Not designated as hedging instruments | Commodity Contracts | Other current assets
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross	576	367
Not designated as hedging instruments | Commodity Contracts | Long-term receivables and other assets, net
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross	10	13
Not designated as hedging instruments | Commodity Contracts | Accrued liabilities
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross	654	407
Not designated as hedging instruments | Commodity Contracts | Deferred credits and other liabilities
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross	$ 8	$ 11