Organization, Basis of Presentation and Significant Accounting Policies (Details 5) (USD $) In Millions, unless otherwise specified	12 Months Ended				12 Months Ended				12 Months Ended			12 Months Ended				12 Months Ended
	Dec. 31, 2012		Dec. 31, 2010	Dec. 31, 2011 Scenario, Previously Reported [Member]	Dec. 31, 2012 Regulated Distribution		Dec. 31, 2010 Regulated Distribution	Dec. 31, 2011 Regulated Distribution Scenario, Previously Reported [Member]	Dec. 31, 2012 Regulated Transmission		Dec. 31, 2011 Regulated Transmission Scenario, Previously Reported [Member]	Dec. 31, 2012 Competitive Energy Services		Dec. 31, 2010 Competitive Energy Services	Dec. 31, 2011 Competitive Energy Services Scenario, Previously Reported [Member]	Dec. 31, 2012 Other/Corporate		Dec. 31, 2011 Other/Corporate Scenario, Previously Reported [Member]
Summary of changes in goodwill
Goodwill, Beginning Balance	$ 6,441		$ 5,575	$ 6,441	$ 5,025		$ 5,025	$ 5,551			$ 0	$ 890		$ 24	$ 890			$ 0
Purchase Accounting Adjustments	6				0				0			6				0
Segment Reorganization	0	[1]			(526)	[1]			526	[1]		0	[1]			0	[1]
Goodwill, Ending Balance	$ 6,447		$ 5,575	$ 6,441	$ 5,025		$ 5,025	$ 5,551	$ 526		$ 0	$ 896		$ 24	$ 890	$ 0		$ 0

[1] Note 18, Segment Information discusses the modification of reporting segments that occurred during 2012 that resulted in the transfer of goodwill from Regulated Distribution to Regulated Transmission.