Supplemental Disclosures About Natural Gas, Oil and NGL Producing Activities (Results of Opeartions (Table) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Supplemental Disclosures About Natural Gas, Oil and NGL (Results of Operations Table) [Abstract]
Natural gas, oil and NGL	$ 6,278	$ 6,024	$ 5,647
Natural gas, oil and NGL production	(1,304)	(1,073)	(893)
Production taxes	(188)	(192)	(157)
Impairment of Natural Gas and Oil Properties	(3,315)	0	0
Natural gas, oil and NGL depreciation, depletion and amortization	(2,507)	(1,632)	(1,394)
Imputed income tax provision	404	(1,220)	(1,233)
Results of Operations, Oil and Gas Producing Activities Net Income (Excluding Corporate Overhead and Interest Costs)	$ (632)	$ 1,907	$ 1,970