Financial and Other Derivative Instruments Financial and Other Derivative Instruments (Netting Offsets Reconciliation to Balance Sheet) (Details) - USD ($)	Jun. 30, 2015	Dec. 31, 2014
Derivative Assets
Derivative asset, gross	$ 607,000,000	$ 1,178,000,000
Collateral adjustment		0
Derivative assets, current	89,000,000	128,000,000
Derivative assets, noncurrent	36,000,000	44,000,000
Derivative Liabilities
Derivative liability, gross	(601,000,000)	(1,110,000,000)
Collateral adjustment	35,000,000	19,000,000
Derivative liabilities, current	(62,000,000)	(77,000,000)
Derivative liabilities, noncurrent	(22,000,000)	(8,000,000)
Current derivative asset
Derivative Assets
Derivative asset, gross	506,000,000	1,083,000,000
Counterparty netting	(417,000,000)	(955,000,000)
Collateral adjustment	0	0
Noncurrent derivative asset
Derivative Assets
Derivative asset, gross	101,000,000	95,000,000
Counterparty netting	(65,000,000)	(51,000,000)
Collateral adjustment	0	0
Current derivative liability
Derivative Liabilities
Derivative liability, gross	(501,000,000)	(1,041,000,000)
Counterparty netting	417,000,000	955,000,000
Collateral adjustment	22,000,000	9,000,000
Noncurrent derivative liability
Derivative Liabilities
Derivative liability, gross	(100,000,000)	(69,000,000)
Counterparty netting	65,000,000	51,000,000
Collateral adjustment	$ 13,000,000	$ 10,000,000