Acquisitions and Divestitures Acquisitions and Divestitures (Components of Discontinued Operations) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Oil and gas	$ 967		$ 820		$ 2,795		$ 2,296
Interest and other	2		8		9		3
Gain on disposition of assets, net	(1)		1		(11)		(206)
Oil and gas production	168		150		493		440
Production and ad valorem taxes	58		49		169		147
Depletion, depreciation and amortization	274		222		734		650
Exploration and abandonment	22		30		80		65
General and administrative	81		72		244		200
Asset Retirement Obligation, Accretion Expense	3		3		9		9
Other Nonoperating Expense	20		24		55		65
Costs and Expenses	866		680		2,457		1,911
Current tax provision	14		9		(4)		(5)
Deferred tax (provision) benefit	(250)		(57)		(315)		(276)
Income (Loss) from Discontinued Operations, Net of Tax	(37)		19		(113)		52
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Oil and gas	49		89		198		246
Interest and other	1	[1]	13	[1]	31	[1]	39	[1]
Gain on disposition of assets, net	0		0		(5)		(9)
Total Revenues And Other Income From Discontinued Operations	50		102		234		294
Oil and gas production	16		32		59		90
Production and ad valorem taxes	3		5		12		15
Depletion, depreciation and amortization	2		34		11		87
Impairment of oil and gas properties	80		0		305		0
Exploration and abandonment	1		2		3		18
General and administrative	0		2		3		4
Asset Retirement Obligation, Accretion Expense	0		0		1		1
Other Nonoperating Expense	6		(2)		14		(2)
Costs and Expenses	108		73		408		213
Income (loss) from discontinued operations before income taxes	(58)		29		(174)		81
Current tax provision	0		0		(1)		(4)
Deferred tax (provision) benefit	21		(10)		62		(25)
Income (Loss) from Discontinued Operations, Net of Tax	$ (37)		$ 19		$ (113)		$ 52

[1] (a)Primarily comprised of cash received associated with Alaskan Petroleum Production Tax credits on qualifying capital expenditures.