Derivative and Hedging Activities Cash Flow Hedge Instruments Gain Loss in Statement of Financial Performance Table (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Cash Flow Hedge Effectiveness Total	$ 3	$ 4	$ 3	$ 4
Natural Gas, Oil and NGL sales
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Cash Flow Hedge Effectiveness Total	(3)	9	(21)	28
Commodity contracts | Natural Gas, Oil and NGL sales
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from AOCI Effective Portion):	(3)	9	(21)	28
Foreign currency contracts | Accumulated Other Comprehensive Income (Loss) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from AOCI Effective Portion):	$ 3	$ 4	$ 3	$ 4