Derivatives and Hedge Accounting Activities (Selected Information Related to Gains (Losses) on Cash Flow Hedges Included in AOCI) (Details) (USD $) In Millions	6 Months Ended
	Jun. 30, 2011
AOCI After-Tax	$ (27)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	(11)
Commodity Contract [Member] | Gas Energy Contract [Member]
AOCI After-Tax	(14)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	(5)
Maximum Term	42 months
Commodity Contract [Member] | Electricity Energy Contract [Member]
AOCI After-Tax	42
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	30
Maximum Term	54 months
Commodity Contract [Member] | NGLs Contract [Member]
AOCI After-Tax	(75)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	(32)
Maximum Term	42 months
Commodity Contract [Member] | Other Energy Contract [Member]
AOCI After-Tax	6
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	2
Maximum Term	47 months
Interest Rate Contract [Member]
AOCI After-Tax	14
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	$ (6)
Maximum Term	378 months