Financial and Derivative Instruments (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011 cubicFeet gal	Jun. 30, 2010	Dec. 31, 2010
Estimated fair value of total long-term debt including capitalized lease obligations	$ 12,600,000,000		$ 12,600,000,000		$ 12,800,000,000
Recorded book values of total long-term debt including capitalized lease obligations	12,123,000,000		12,123,000,000		12,227,000,000
Derivative assets at fair value, net	155,000,000		155,000,000		172,000,000
Gain (loss) before-tax earnings impact of derivatives	39,000,000	24,000,000	59,000,000	33,000,000
Volume (Cubic feet daily)			250,000,000
Weighted average NYMEX price (per thousand cubic feet)			$ 7.02
Cash Flow Hedge [Member]
Derivative assets at fair value, net	114,000,000		114,000,000
Gain (loss) before-tax earnings impact of derivatives			$ 56,000,000