Derivative and Hedging Activities Cash Flow Hedge Instruments Gain Loss in Statement of Financial Performance (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain Loss On Cash Flow Hedge Effectiveness Total	$ 2	$ (5)	$ 0	$ 0
Natural Gas, Oil and NGL sales
Derivative Instruments, Gain (Loss) [Line Items]
Gain Loss On Cash Flow Hedge Effectiveness Total	1	17	(18)	19
Commodity contracts | Natural Gas, Oil and NGL sales
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from AOCI into Income (Effective Portion)	1	17	(18)	19
Foreign currency contracts | Accumulated Other Comprehensive Income (Loss) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	$ 2	$ (5)	$ 0	$ 0