Derivatives (Details 2) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Gross and net fair values of outstanding derivatives (in millions)
Collateral received netted against derivative assets	$ 0	$ 14
Collateral paid netted against derivative liabilities	29	4
Collateral deposited with clearinghouses and brokers	33	3
Cash-flow hedges | Other current assets
Gross and net fair values of outstanding derivatives (in millions)
Total net fair value, asset		9
Cash-flow hedges | Accrued liabilities
Gross and net fair values of outstanding derivatives (in millions)
Total net fair value, liability	1
Cash-flow hedges | Other Liabilities
Gross and net fair values of outstanding derivatives (in millions)
Total net fair value, liability		1
Not designated as hedging instruments
Gross and net fair values of outstanding derivatives (in millions)
Less: counterparty netting and cash collateral, asset	(498)	(535)
Less: counterparty netting and cash collateral, liability	(527)	(525)
Total net fair value, asset	45	109
Total net fair value, liability	385	423
Not designated as hedging instruments | Other current assets
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross	535	626
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	9
Not designated as hedging instruments | Accrued liabilities
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross	618	672
Not designated as hedging instruments | Other Liabilities
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		947
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	293	275
Not designated as hedging instruments | Other assets
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		635
Total net fair value, asset	543
Total net fair value, liability	911
Not designated as hedging instruments | Commodity Contracts
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross	543	644
Commodity contract derivative liability, gross	$ 912	$ 948