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, 2014
Derivative Instruments, Gain (Loss) [Line Items]
AOCI After-Tax	$ (278)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	(158)
Commodity | Gas Energy Contract
Derivative Instruments, Gain (Loss) [Line Items]
AOCI After-Tax	(6)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	(6)
Maximum Term	25 months
Commodity | Electricity Energy Contract
Derivative Instruments, Gain (Loss) [Line Items]
AOCI After-Tax	(135)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	(145)
Maximum Term	33 months
Commodity | Other Energy Contract
Derivative Instruments, Gain (Loss) [Line Items]
AOCI After-Tax	0
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	0
Maximum Term	26 months
Interest rate
Derivative Instruments, Gain (Loss) [Line Items]
AOCI After-Tax	(137)
Amounts Expected to be Reclassified to Earnings during the next 12 Months After-Tax	$ (7)
Maximum Term	366 months