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	6 Months Ended
	Jun. 30, 2012
AOCI After-Tax	$ 29
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	51
Commodity Contract | Gas Energy Contract
AOCI After-Tax	(26)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	(18)
Maximum Length of Time Hedged in Cash Flow Hedge	30 months
Commodity Contract | Electricity Energy Contract
AOCI After-Tax	180
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	68
Maximum Length of Time Hedged in Cash Flow Hedge	42 months
Commodity Contract | NGLs Contract
AOCI After-Tax	34
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	12
Maximum Length of Time Hedged in Cash Flow Hedge	30 months
Commodity Contract | Other Energy Contract
AOCI After-Tax	5
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	3
Maximum Length of Time Hedged in Cash Flow Hedge	47 months
Interest Rate Contract
AOCI After-Tax	(164)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	$ (14)
Maximum Length of Time Hedged in Cash Flow Hedge	366 months