Derivative And Hedging Activities (Schedule Of Cash Flow Hedge Instruments, Gain (Loss) In Statement Of Financial Performance) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
AOCI [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) On Cash Flow Hedge (Effectiveness Portion) Total	$ 6	$ (2)
Natural Gas And Oil Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized, Commodity Contracts, Ineffective Portion		10
Gain (Loss) Recognized, Amount initially excluded from effectiveness testing		22
Gain (Loss) Recognized in Income, Commodity contracts		32
Commodity Contracts [Member] | AOCI [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in AOCI (Effective Portion)	1	16
Commodity Contracts [Member] | Natural Gas And Oil Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from AOCI into Income (Effective Portion)	3	74
Foreign Currency Contracts [Member] | AOCI [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in AOCI (Effective Portion)	$ 5	$ (18)