Derivative and Hedging Activities Derivatives Not Designated as Hedging Instruments 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
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in net income (loss)	$ 3	$ 2	$ (51)	$ 4
Not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in net income (loss)	(248)	(36)	107	794
Not designated as hedging instruments | Commodity contracts | Natural Gas, Oil and NGL sales
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in net income (loss)	(250)	(36)	162	796
Not designated as hedging instruments | Interest rate contract | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in net income (loss)	$ 2	$ 0	$ (55)	$ (2)