Derivative and Hedging Activities - Natural Gas and Oil Sales Table (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Natural gas, oil and NGL Sales	$ 1,766	$ 1,453
Natural Gas, Oil and NGL [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Natural gas, oil and NGL sales	2,148	1,595
Losses on undesignated natural gas, oil and NGL derivatives	(365)	(123)
Losses on terminated cash flow hedges	(17)	(19)
Natural gas, oil and NGL Sales	$ 1,766	$ 1,453