Derivatives and Hedge Accounting Activities (Selected Information Related to Gains (Losses) on Cash Flow Hedges Included in AOCI) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
AOCI After-Tax	$ (77)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	0
Commodity Contract | Gas Energy Contract
AOCI After-Tax	(27)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	(23)
Maximum Length of Time Hedged in Cash Flow Hedge	27 months
Commodity Contract | Electricity Energy Contract
AOCI After-Tax	108
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	39
Maximum Length of Time Hedged in Cash Flow Hedge	39 months
Commodity Contract | NGLs Contract
AOCI After-Tax	9
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	3
Maximum Length of Time Hedged in Cash Flow Hedge	27 months
Commodity Contract | Other Energy Contract
AOCI After-Tax	4
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	3
Maximum Length of Time Hedged in Cash Flow Hedge	44 months
Interest Rate Contract
AOCI After-Tax	(171)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	$ (22)
Maximum Length of Time Hedged in Cash Flow Hedge	360 months