Acquisitions and Divestitures Acquisitions and Divestitures (Components of Discontinued Operations) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Oil and gas	$ 910		$ 729
Interest and other	4		0
Oil and gas production	165		150
Production and ad valorem taxes	57		52
Depletion, depreciation and amortization	221		212
Exploration and abandonment	31		18
General and administrative	81		62
Other Nonoperating Expense	15		20
Costs and Expenses	761		624
Current Income Tax (Expense) Benefit	(12)		(6)
Deferred Income Tax (Expense) Benefit	(41)		(44)
Income (Loss) from Discontinued Operations, Net of Tax	(26)		16
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Oil and gas	68		60
Interest and other	29	[1]	19	[1]
Total Revenues And Other Income From Discontinued Operations	97		79
Oil and gas production	18		20
Production and ad valorem taxes	3		3
Depletion, depreciation and amortization	0		19
Impairment of oil and gas properties	111		0
Exploration and abandonment	1		10
General and administrative	2		2
Other Nonoperating Expense	3		0
Costs and Expenses	138		54
Income (Loss) from Discontinued Operation, before Income Tax	(41)		25
Current Income Tax (Expense) Benefit	0		(1)
Deferred Income Tax (Expense) Benefit	15		(8)
Income (Loss) from Discontinued Operations, Net of Tax	$ (26)		$ 16

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