Fair Value Measurements (Fair Value, Assets And Liabilities, Unobservable Input Reconciliation) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Commodity Contracts [Member]
Beginning balance	$ (1,654)		$ (1,954)
Total gains (losses) Included in earnings or change in net assets	(59)	[1]	(873)	[1]
Settlements	8		44
Ending balance	(1,705)		(2,783)
Interest Rate Contracts [Member]
Beginning balance			(69)
Total gains (losses) Included in earnings or change in net assets	(1)	[1]	16	[1]
Sales	(2)
Settlements			(1)
Transfers in and out of Level 3			54	[2]
Ending balance	(3)
Foreign Currency Contracts [Member]
Beginning balance			(43)
Transfers in and out of Level 3			43	[2]
Debt [Member]
Beginning balance			(1,371)
Transfers in and out of Level 3			1,371	[2]
Natural Gas And Oil Sales [Member]
Total gains (losses) Included in earnings or change in net assets	(59)		(873)
Change in unrealized gains (losses) relating to assets still held at reporting date	(132)		(868)
Interest Expense [Member]
Total gains (losses) Included in earnings or change in net assets	(1)		16
Change in unrealized gains (losses) relating to assets still held at reporting date	$ (3)		$ 2

[1] Natural GasInterestand Oil SalesExpense2012201120122011($ in millions) Total gains (losses) included in earnings
(or change in net assets) for the period $(59) $(873) $(1) $16 Change in unrealized gains (losses) relating to
assets still held at reporting date $(132) $(868) $(3) $2

[2] The values related to interest rate and cross currency swaps were transferred from Level 3 to Level 2 as a result of our ability to use data readily available in the public market to corroborate our estimated fair values.