Organization, Basis of Presentation and Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Regulatory assets on the Balance Sheets
Regulatory Assets	$ 1,411	$ 1,854
Increase (Decrease)	(443)
Regulatory transition costs
Regulatory assets on the Balance Sheets
Regulatory Assets	240	266
Increase (Decrease)	(26)
Customer receivables for future income taxes
Regulatory assets on the Balance Sheets
Regulatory Assets	370	518
Increase (Decrease)	(148)
Nuclear decommissioning and spent fuel disposal costs
Regulatory assets on the Balance Sheets
Regulatory Assets	(305)	(198)
Increase (Decrease)	(107)
Asset removal costs
Regulatory assets on the Balance Sheets
Regulatory Assets	(254)	(362)
Increase (Decrease)	108
Deferred transmission costs
Regulatory assets on the Balance Sheets
Regulatory Assets	90	112
Increase (Decrease)	(22)
Deferred generation costs
Regulatory assets on the Balance Sheets
Regulatory Assets	281	346
Increase (Decrease)	(65)
Deferred distribution costs
Regulatory assets on the Balance Sheets
Regulatory Assets	182	194
Increase (Decrease)	(12)
Contract valuations
Regulatory assets on the Balance Sheets
Regulatory Assets	153	260
Increase (Decrease)	(107)
Storm-related costs
Regulatory assets on the Balance Sheets
Regulatory Assets	465	455
Increase (Decrease)	10
Other
Regulatory assets on the Balance Sheets
Regulatory Assets	189	263
Increase (Decrease)	$ (74)