Derivatives and Hedge Accounting Activities (Selected Information Related to Gains (Losses) on Cash Flow Hedges Included in AOCI) (Details) (USD $) In Millions	9 Months Ended
	Sep. 30, 2011
AOCI After-Tax	(121)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	(14)
Commodity Contract [Member]
Maximum Length of Time Hedged in Cash Flow Hedge	44 months
Commodity Contract [Member] | Gas Energy Contract [Member]
AOCI After-Tax	(19)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	(7)
Maximum Length of Time Hedged in Cash Flow Hedge	39 months
Commodity Contract [Member] | Electricity Energy Contract [Member]
AOCI After-Tax	38
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	21
Maximum Length of Time Hedged in Cash Flow Hedge	51 months
Commodity Contract [Member] | NGLs Contract [Member]
AOCI After-Tax	(39)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	(24)
Maximum Length of Time Hedged in Cash Flow Hedge	39 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	1
Interest Rate Contract [Member]
AOCI After-Tax	(107)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	(5)
Maximum Length of Time Hedged in Cash Flow Hedge	375 months