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	12 Months Ended
	Dec. 31, 2011
AOCI After-Tax	(54)
Amounts expected to be reclassified to earnings during the next 12 months after-tax	(1)
Commodity Contract [Member]
Maximum Length of Time Hedged in Cash Flow Hedge	41 months
Commodity Contract [Member] | Gas Energy Contract [Member]
AOCI After-Tax	(33)
Amounts expected to be reclassified to earnings during the next 12 months after-tax	(25)
Maximum Length of Time Hedged in Cash Flow Hedge	36 months
Commodity Contract [Member] | Electricity Energy Contract [Member]
AOCI After-Tax	146
Amounts expected to be reclassified to earnings during the next 12 months after-tax	53
Maximum Length of Time Hedged in Cash Flow Hedge	48 months
Commodity Contract [Member] | NGL Contract [Member]
AOCI After-Tax	(57)
Amounts expected to be reclassified to earnings during the next 12 months after-tax	(26)
Maximum Length of Time Hedged in Cash Flow Hedge	36 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
Interest Rate Contract [Member]
AOCI After-Tax	(116)
Amounts expected to be reclassified to earnings during the next 12 months after-tax	(5)
Maximum Length of Time Hedged in Cash Flow Hedge	372 months