Employee Benefit Plans (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Contributions by Employer			$ 92
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Impact of remeasurement on liability			(121)
Actuarial loss (gain)			(62)
Defined Benefit Plan, Plan Amendments			(59)
Defined Benefit Plan, Contributions by Employer			6
Estimated Future Employer Contributions in Current Fiscal Year			2
Net regulatory liabilities [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost (credit) for regulatory liabilities	(1)	(2)	(4)	(4)
Amortization of net actuarial (gain) loss for regulatory liabilities	$ 0	$ 1	$ 2	$ 4