Financial and Other Derivative Instruments Financial and Other Derivative Instruments (Details 2) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Derivative [Line Items]
Derivative Assets, Current	$ 72	$ 108
Derivative Assets, Noncurrent	26	39
Derivative Liabilities, Current	(58)	(125)
Derivative Liabilities, Noncurrent	(21)	(26)
Derivative Asset [Member]
Derivative [Line Items]
Derivative Assets, Current	711	862
Derivative Assets, Noncurrent	132	154
Derivative Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities, Current	(668)	(879)
Derivative Liabilities, Noncurrent	(147)	(141)
Counterparty Netting [Member]
Derivative [Line Items]
Derivative Assets, Current	(610)	(754)
Derivative Assets, Noncurrent	(106)	(115)
Derivative Liabilities, Current	(610)	(754)
Derivative Liabilities, Noncurrent	(106)	(115)
Collateral Adjustment [Member]
Derivative [Line Items]
Derivative Assets, Current	(29)	0
Derivative Assets, Noncurrent	0	0
Derivative Liabilities, Current	0	0
Derivative Liabilities, Noncurrent	(20)	0
Derivative [Member]
Derivative [Line Items]
Derivative Assets, Current	72	108
Derivative Assets, Noncurrent	26	39
Derivative Liabilities, Current	(58)	(125)
Derivative Liabilities, Noncurrent	$ (21)	$ (26)

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References+ Details

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled after one year or the normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References+ Details

- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References+ Details

- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled after one year or the normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References+ Details