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	3 Months Ended
	Mar. 31, 2012
AOCI After-Tax	$ 58
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	49
Commodity Contract | Gas Energy Contract
AOCI After-Tax	(30)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	(16)
Maximum Length of Time Hedged in Cash Flow Hedge	33 months
Commodity Contract | Electricity Energy Contract
AOCI After-Tax	243
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	102
Maximum Length of Time Hedged in Cash Flow Hedge	45 months
Commodity Contract | NGLs Contract
AOCI After-Tax	(64)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	(27)
Maximum Length of Time Hedged in Cash Flow Hedge	33 months
Commodity Contract | Other Energy Contract
AOCI After-Tax	6
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	2
Maximum Length of Time Hedged in Cash Flow Hedge	38 months
Interest Rate Contract
AOCI After-Tax	(97)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	$ (12)
Maximum Length of Time Hedged in Cash Flow Hedge	369 months