Income Taxes (Deferred Tax Assets (Liabilities)) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Components of Deferred Tax Assets and Liabilities [Abstract]
Property, plant and equipment	$ (3,372)	$ (3,389)
Securitized regulatory assets	(127)	(256)
Alternative minimum tax credit carry-forwards	266	254
Merger basis differences	18	42
Pension and benefits	(30)	(33)
Other comprehensive income	0	101
Derivative assets liabilities	0	66
State net operating loss and credit carry-forwards	43	37
Deferred Tax Liabilities, Other	(110)
Other		41
Deferred Tax Liabilities, Gross	(3,312)	(3,137)
Less valuation allowance	(37)	(33)
Current deferred income tax assets	(28)	21
Long-term deferred income tax liabilities	(3,321)	(3,191)
Deferred Tax Assets, Net of Valuation Allowance	1,808	1,038
Deferred Tax Liability, Net of Valuation Allowance	(5,157)	(4,208)
Deferred income tax liabilities	$ (3,349)	$ (3,170)