Financial and Other Derivative Instruments (Details Textuals) (USD $) In Millions, unless otherwise specified			3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 FTR [Member]	Mar. 31, 2013 FTR [Member]	Mar. 31, 2014 Credit Risk Contract [Member]
Derivative [Line Items]
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	$ 1
Letters of Credit Outstanding, Amount	18	19
Cash Collateral Posted Net of Cash Collateral Received	128	12
Cash Collateral Paid or Received for Derivative Assets	6	26
Cash Collateral Paid or Received for Derivative Liabilities	4	17
Cash Collateral Received	10	13
Cash Collateral Paid	140	34
Effect of Derivative Instruments Recoverable Through PSCR Mechanism			4	1
Value of Transactions Company Would Have Been Exposed to if Credit Rating Below Investment Grade	444
Derivative, Net Liability Position, Aggregate Fair Value	1,089
Collateral Already Posted, Aggregate Fair Value	959				15
Additional Collateral, Aggregate Fair Value	$ 115