Regulatory Assets, Liabilities, And Balancing Accounts (Current Regulatory Balancing Accounts, Net) (Details) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Regulatory Assets [Line Items]
Current regulatory balancing accounts, net	$ 642	$ 849
Utility Generation [Member]
Regulatory Assets [Line Items]
Current regulatory balancing accounts, net	173	303
Distribution Revenue Adjustment Mechanism [Member]
Regulatory Assets [Line Items]
Current regulatory balancing accounts, net	145	145
Gas Fixed Cost [Member]
Regulatory Assets [Line Items]
Current regulatory balancing accounts, net	115	56
Public Purpose Programs [Member]
Regulatory Assets [Line Items]
Current regulatory balancing accounts, net	98	164
Hazardous Substance [Member]
Regulatory Assets [Line Items]
Current regulatory balancing accounts, net	57	38
Energy Recovery Bonds [Member]
Regulatory Assets [Line Items]
Current regulatory balancing accounts, net	(118)	(34)
Energy Procurement Costs [Member]
Regulatory Assets [Line Items]
Current regulatory balancing accounts, net	(70)	(25)
Other Current Balancing Accounts [Member]
Regulatory Assets [Line Items]
Current regulatory balancing accounts, net	$ 242	$ 202